├── app
├── .gitignore
├── src
│ ├── main
│ │ ├── res
│ │ │ ├── values
│ │ │ │ ├── strings.xml
│ │ │ │ ├── colors.xml
│ │ │ │ └── themes.xml
│ │ │ ├── mipmap-hdpi
│ │ │ │ ├── ic_launcher.webp
│ │ │ │ └── ic_launcher_round.webp
│ │ │ ├── mipmap-mdpi
│ │ │ │ ├── ic_launcher.webp
│ │ │ │ └── ic_launcher_round.webp
│ │ │ ├── mipmap-xhdpi
│ │ │ │ ├── ic_launcher.webp
│ │ │ │ └── ic_launcher_round.webp
│ │ │ ├── mipmap-xxhdpi
│ │ │ │ ├── ic_launcher.webp
│ │ │ │ └── ic_launcher_round.webp
│ │ │ ├── mipmap-xxxhdpi
│ │ │ │ ├── ic_launcher.webp
│ │ │ │ └── ic_launcher_round.webp
│ │ │ ├── mipmap-anydpi-v26
│ │ │ │ ├── ic_launcher.xml
│ │ │ │ └── ic_launcher_round.xml
│ │ │ ├── values-night
│ │ │ │ └── themes.xml
│ │ │ ├── drawable-v24
│ │ │ │ └── ic_launcher_foreground.xml
│ │ │ ├── layout
│ │ │ │ └── activity_main.xml
│ │ │ └── drawable
│ │ │ │ └── ic_launcher_background.xml
│ │ ├── java
│ │ │ └── com
│ │ │ │ └── example
│ │ │ │ └── myapplication
│ │ │ │ ├── IndexScroller.java
│ │ │ │ ├── SnapPreference.java
│ │ │ │ ├── SmoothIndexScroller.java
│ │ │ │ ├── Rangefinder.java
│ │ │ │ ├── ImmediateIndexScroller.java
│ │ │ │ └── MainActivity.java
│ │ └── AndroidManifest.xml
│ ├── test
│ │ └── java
│ │ │ └── com
│ │ │ └── example
│ │ │ └── myapplication
│ │ │ └── ExampleUnitTest.java
│ └── androidTest
│ │ └── java
│ │ └── com
│ │ └── example
│ │ └── myapplication
│ │ └── ExampleInstrumentedTest.java
├── proguard-rules.pro
└── build.gradle
├── .idea
├── .name
├── .gitignore
├── compiler.xml
├── vcs.xml
├── deploymentTargetDropDown.xml
├── migrations.xml
├── misc.xml
└── gradle.xml
├── gradle
└── wrapper
│ ├── gradle-wrapper.jar
│ └── gradle-wrapper.properties
├── .gitignore
├── settings.gradle
├── gradle.properties
├── gradlew.bat
└── gradlew
/app/.gitignore:
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1 | /build
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/.idea/.name:
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1 | My Application
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/.idea/.gitignore:
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1 | # Default ignored files
2 | /shelf/
3 | /workspace.xml
4 |
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/app/src/main/res/values/strings.xml:
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1 |
2 | My Application
3 |
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/gradle/wrapper/gradle-wrapper.jar:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/gradle/wrapper/gradle-wrapper.jar
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/app/src/main/res/mipmap-hdpi/ic_launcher.webp:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/app/src/main/res/mipmap-hdpi/ic_launcher.webp
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/app/src/main/res/mipmap-mdpi/ic_launcher.webp:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/app/src/main/res/mipmap-mdpi/ic_launcher.webp
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/app/src/main/res/mipmap-xhdpi/ic_launcher.webp:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/app/src/main/res/mipmap-xhdpi/ic_launcher.webp
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/app/src/main/res/mipmap-xxhdpi/ic_launcher.webp:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/app/src/main/res/mipmap-xxhdpi/ic_launcher.webp
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/app/src/main/res/mipmap-xxxhdpi/ic_launcher.webp:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/app/src/main/res/mipmap-xxxhdpi/ic_launcher.webp
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/app/src/main/res/mipmap-hdpi/ic_launcher_round.webp:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/app/src/main/res/mipmap-hdpi/ic_launcher_round.webp
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/app/src/main/res/mipmap-mdpi/ic_launcher_round.webp:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/app/src/main/res/mipmap-mdpi/ic_launcher_round.webp
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/app/src/main/res/mipmap-xhdpi/ic_launcher_round.webp:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/app/src/main/res/mipmap-xhdpi/ic_launcher_round.webp
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/app/src/main/res/mipmap-xxhdpi/ic_launcher_round.webp:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/app/src/main/res/mipmap-xxhdpi/ic_launcher_round.webp
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/app/src/main/res/mipmap-xxxhdpi/ic_launcher_round.webp:
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https://raw.githubusercontent.com/benioZhang/recyclerView-scroll-demo/HEAD/app/src/main/res/mipmap-xxxhdpi/ic_launcher_round.webp
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/.idea/compiler.xml:
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/.idea/vcs.xml:
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/gradle/wrapper/gradle-wrapper.properties:
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1 | distributionBase=GRADLE_USER_HOME
2 | distributionPath=wrapper/dists
3 | distributionUrl=https\://services.gradle.org/distributions/gradle-7.2-bin.zip
4 | zipStoreBase=GRADLE_USER_HOME
5 | zipStorePath=wrapper/dists
6 |
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/app/src/main/java/com/example/myapplication/IndexScroller.java:
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1 | package com.example.myapplication;
2 |
3 | public interface IndexScroller {
4 | void scrollToPosition(int position);
5 |
6 | void scrollToPosition(int position, @SnapPreference int snapPreference);
7 | }
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/.idea/deploymentTargetDropDown.xml:
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/.gitignore:
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1 | *.iml
2 | .gradle
3 | /local.properties
4 | /.idea/caches
5 | /.idea/libraries
6 | /.idea/modules.xml
7 | /.idea/workspace.xml
8 | /.idea/navEditor.xml
9 | /.idea/assetWizardSettings.xml
10 | .DS_Store
11 | /build
12 | /captures
13 | .externalNativeBuild
14 | .cxx
15 | local.properties
16 |
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/.idea/migrations.xml:
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/app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml:
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/app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml:
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/settings.gradle:
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1 | dependencyResolutionManagement {
2 | repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
3 | repositories {
4 | google()
5 | mavenCentral()
6 | jcenter() // Warning: this repository is going to shut down soon
7 | }
8 | }
9 | rootProject.name = "My Application"
10 | include ':app'
11 |
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/app/src/main/res/values/colors.xml:
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1 |
2 |
3 | #FFBB86FC
4 | #FF6200EE
5 | #FF3700B3
6 | #FF03DAC5
7 | #FF018786
8 | #FF000000
9 | #FFFFFFFF
10 |
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/app/src/test/java/com/example/myapplication/ExampleUnitTest.java:
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1 | package com.example.myapplication;
2 |
3 | import org.junit.Test;
4 |
5 | import static org.junit.Assert.*;
6 |
7 | /**
8 | * Example local unit test, which will execute on the development machine (host).
9 | *
10 | * @see Testing documentation
11 | */
12 | public class ExampleUnitTest {
13 | @Test
14 | public void addition_isCorrect() {
15 | assertEquals(4, 2 + 2);
16 | }
17 | }
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/.idea/misc.xml:
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15 |
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/.idea/gradle.xml:
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19 |
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/app/proguard-rules.pro:
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1 | # Add project specific ProGuard rules here.
2 | # You can control the set of applied configuration files using the
3 | # proguardFiles setting in build.gradle.
4 | #
5 | # For more details, see
6 | # http://developer.android.com/guide/developing/tools/proguard.html
7 |
8 | # If your project uses WebView with JS, uncomment the following
9 | # and specify the fully qualified class name to the JavaScript interface
10 | # class:
11 | #-keepclassmembers class fqcn.of.javascript.interface.for.webview {
12 | # public *;
13 | #}
14 |
15 | # Uncomment this to preserve the line number information for
16 | # debugging stack traces.
17 | #-keepattributes SourceFile,LineNumberTable
18 |
19 | # If you keep the line number information, uncomment this to
20 | # hide the original source file name.
21 | #-renamesourcefileattribute SourceFile
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/app/src/main/AndroidManifest.xml:
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23 |
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/app/src/main/res/values/themes.xml:
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/app/src/main/res/values-night/themes.xml:
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1 |
2 |
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16 |
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/app/src/androidTest/java/com/example/myapplication/ExampleInstrumentedTest.java:
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1 | package com.example.myapplication;
2 |
3 | import android.content.Context;
4 |
5 | import androidx.test.platform.app.InstrumentationRegistry;
6 | import androidx.test.ext.junit.runners.AndroidJUnit4;
7 |
8 | import org.junit.Test;
9 | import org.junit.runner.RunWith;
10 |
11 | import static org.junit.Assert.*;
12 |
13 | /**
14 | * Instrumented test, which will execute on an Android device.
15 | *
16 | * @see Testing documentation
17 | */
18 | @RunWith(AndroidJUnit4.class)
19 | public class ExampleInstrumentedTest {
20 | @Test
21 | public void useAppContext() {
22 | // Context of the app under test.
23 | Context appContext = InstrumentationRegistry.getInstrumentation().getTargetContext();
24 | assertEquals("com.example.myapplication", appContext.getPackageName());
25 | }
26 | }
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/gradle.properties:
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1 | # Project-wide Gradle settings.
2 | # IDE (e.g. Android Studio) users:
3 | # Gradle settings configured through the IDE *will override*
4 | # any settings specified in this file.
5 | # For more details on how to configure your build environment visit
6 | # http://www.gradle.org/docs/current/userguide/build_environment.html
7 | # Specifies the JVM arguments used for the daemon process.
8 | # The setting is particularly useful for tweaking memory settings.
9 | org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
10 | # When configured, Gradle will run in incubating parallel mode.
11 | # This option should only be used with decoupled projects. More details, visit
12 | # http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
13 | # org.gradle.parallel=true
14 | # AndroidX package structure to make it clearer which packages are bundled with the
15 | # Android operating system, and which are packaged with your app"s APK
16 | # https://developer.android.com/topic/libraries/support-library/androidx-rn
17 | android.useAndroidX=true
18 | # Automatically convert third-party libraries to use AndroidX
19 | android.enableJetifier=true
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/app/build.gradle:
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1 | plugins {
2 | id 'com.android.application'
3 | }
4 |
5 | android {
6 | compileSdk 33
7 |
8 | defaultConfig {
9 | applicationId "com.example.myapplication"
10 | minSdk 21
11 | targetSdk 33
12 | versionCode 1
13 | versionName "1.0"
14 |
15 | testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
16 | }
17 |
18 | buildTypes {
19 | release {
20 | minifyEnabled false
21 | proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
22 | }
23 | }
24 | compileOptions {
25 | sourceCompatibility JavaVersion.VERSION_1_8
26 | targetCompatibility JavaVersion.VERSION_1_8
27 | }
28 | }
29 |
30 | dependencies {
31 |
32 | implementation 'androidx.appcompat:appcompat:1.6.1'
33 | implementation 'com.google.android.material:material:1.6.0'
34 | implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
35 | testImplementation 'junit:junit:4.+'
36 | androidTestImplementation 'androidx.test.ext:junit:1.1.5'
37 | androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
38 | }
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/app/src/main/java/com/example/myapplication/SnapPreference.java:
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1 | package com.example.myapplication;
2 |
3 | import androidx.annotation.IntDef;
4 | import androidx.recyclerview.widget.LinearSmoothScroller;
5 |
6 | import java.lang.annotation.Retention;
7 | import java.lang.annotation.RetentionPolicy;
8 |
9 | @Retention(RetentionPolicy.SOURCE)
10 | @IntDef(value = {
11 | SnapPreference.SNAP_TO_START,
12 | SnapPreference.SNAP_TO_ANY,
13 | SnapPreference.SNAP_TO_END,
14 | SnapPreference.SNAP_TO_CENTER
15 | })
16 | public @interface SnapPreference {
17 | /**
18 | * Align child view's left or top with parent view's left or top
19 | */
20 | int SNAP_TO_START = LinearSmoothScroller.SNAP_TO_START;
21 |
22 | /**
23 | *
Decides if the child should be snapped from start or end, depending on where it
24 | * currently is in relation to its parent.
25 | * For instance, if the view is virtually on the left of RecyclerView, using
26 | * {@code SNAP_TO_ANY} is the same as using {@code SNAP_TO_START}
27 | */
28 | int SNAP_TO_ANY = LinearSmoothScroller.SNAP_TO_ANY;
29 |
30 | /**
31 | * Align child view's right or bottom with parent view's right or bottom
32 | */
33 | int SNAP_TO_END = LinearSmoothScroller.SNAP_TO_END;
34 |
35 | /**
36 | * Align child view's center with parent view's center
37 | */
38 | int SNAP_TO_CENTER = 2;
39 | }
40 |
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/app/src/main/res/drawable-v24/ic_launcher_foreground.xml:
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1 |
7 |
8 |
9 |
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18 |
21 |
22 |
23 |
24 |
30 |
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/app/src/main/java/com/example/myapplication/SmoothIndexScroller.java:
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1 | package com.example.myapplication;
2 |
3 | import android.content.Context;
4 |
5 | import androidx.annotation.NonNull;
6 | import androidx.recyclerview.widget.LinearSmoothScroller;
7 | import androidx.recyclerview.widget.RecyclerView;
8 |
9 | public class SmoothIndexScroller implements IndexScroller {
10 | private final RecyclerView mRecyclerView;
11 |
12 | public SmoothIndexScroller(@NonNull RecyclerView recyclerView) {
13 | mRecyclerView = recyclerView;
14 | }
15 |
16 | @NonNull
17 | protected RecyclerView.SmoothScroller createScroller(@NonNull RecyclerView recyclerView, @SnapPreference int snapPreference) {
18 | return new SmoothScroller(recyclerView.getContext(), snapPreference);
19 | }
20 |
21 | @Override
22 | public void scrollToPosition(int position) {
23 | scrollToPosition(position, SnapPreference.SNAP_TO_ANY);
24 | }
25 |
26 | @Override
27 | public void scrollToPosition(int position, @SnapPreference int snapPreference) {
28 | RecyclerView recyclerView = mRecyclerView;
29 | RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
30 | if (layoutManager == null || position < 0) {
31 | return;
32 | }
33 | RecyclerView.SmoothScroller scroller = createScroller(recyclerView, snapPreference);
34 | scroller.setTargetPosition(position);
35 | layoutManager.startSmoothScroll(scroller);
36 | }
37 |
38 | public static class SmoothScroller extends LinearSmoothScroller {
39 | private final int mVerticalSnapPreference;
40 | private final int mHorizontalSnapPreference;
41 |
42 | public SmoothScroller(Context context, @SnapPreference int snapPreference) {
43 | this(context, snapPreference, snapPreference);
44 | }
45 |
46 | public SmoothScroller(Context context, @SnapPreference int verticalSnapPreference, @SnapPreference int horizontalSnapPreference) {
47 | super(context);
48 | mVerticalSnapPreference = verticalSnapPreference;
49 | mHorizontalSnapPreference = horizontalSnapPreference;
50 | }
51 |
52 | @Override
53 | protected int getVerticalSnapPreference() {
54 | return mVerticalSnapPreference;
55 | }
56 |
57 | @Override
58 | protected int getHorizontalSnapPreference() {
59 | return mHorizontalSnapPreference;
60 | }
61 |
62 | @Override
63 | public int calculateDtToFit(int viewStart, int viewEnd, int boxStart, int boxEnd, int snapPreference) {
64 | if (snapPreference == SnapPreference.SNAP_TO_CENTER) {
65 | return (boxStart + (boxEnd - boxStart) / 2) - (viewStart + (viewEnd - viewStart) / 2);
66 | }
67 | return super.calculateDtToFit(viewStart, viewEnd, boxStart, boxEnd, snapPreference);
68 | }
69 | }
70 | }
71 |
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/gradlew.bat:
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1 | @rem
2 | @rem Copyright 2015 the original author or authors.
3 | @rem
4 | @rem Licensed under the Apache License, Version 2.0 (the "License");
5 | @rem you may not use this file except in compliance with the License.
6 | @rem You may obtain a copy of the License at
7 | @rem
8 | @rem https://www.apache.org/licenses/LICENSE-2.0
9 | @rem
10 | @rem Unless required by applicable law or agreed to in writing, software
11 | @rem distributed under the License is distributed on an "AS IS" BASIS,
12 | @rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 | @rem See the License for the specific language governing permissions and
14 | @rem limitations under the License.
15 | @rem
16 |
17 | @if "%DEBUG%" == "" @echo off
18 | @rem ##########################################################################
19 | @rem
20 | @rem Gradle startup script for Windows
21 | @rem
22 | @rem ##########################################################################
23 |
24 | @rem Set local scope for the variables with windows NT shell
25 | if "%OS%"=="Windows_NT" setlocal
26 |
27 | set DIRNAME=%~dp0
28 | if "%DIRNAME%" == "" set DIRNAME=.
29 | set APP_BASE_NAME=%~n0
30 | set APP_HOME=%DIRNAME%
31 |
32 | @rem Resolve any "." and ".." in APP_HOME to make it shorter.
33 | for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
34 |
35 | @rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
36 | set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
37 |
38 | @rem Find java.exe
39 | if defined JAVA_HOME goto findJavaFromJavaHome
40 |
41 | set JAVA_EXE=java.exe
42 | %JAVA_EXE% -version >NUL 2>&1
43 | if "%ERRORLEVEL%" == "0" goto execute
44 |
45 | echo.
46 | echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
47 | echo.
48 | echo Please set the JAVA_HOME variable in your environment to match the
49 | echo location of your Java installation.
50 |
51 | goto fail
52 |
53 | :findJavaFromJavaHome
54 | set JAVA_HOME=%JAVA_HOME:"=%
55 | set JAVA_EXE=%JAVA_HOME%/bin/java.exe
56 |
57 | if exist "%JAVA_EXE%" goto execute
58 |
59 | echo.
60 | echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
61 | echo.
62 | echo Please set the JAVA_HOME variable in your environment to match the
63 | echo location of your Java installation.
64 |
65 | goto fail
66 |
67 | :execute
68 | @rem Setup the command line
69 |
70 | set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
71 |
72 |
73 | @rem Execute Gradle
74 | "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
75 |
76 | :end
77 | @rem End local scope for the variables with windows NT shell
78 | if "%ERRORLEVEL%"=="0" goto mainEnd
79 |
80 | :fail
81 | rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
82 | rem the _cmd.exe /c_ return code!
83 | if not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
84 | exit /b 1
85 |
86 | :mainEnd
87 | if "%OS%"=="Windows_NT" endlocal
88 |
89 | :omega
90 |
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/app/src/main/res/layout/activity_main.xml:
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/app/src/main/java/com/example/myapplication/Rangefinder.java:
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1 | package com.example.myapplication;
2 |
3 | import android.view.View;
4 |
5 | import androidx.annotation.Nullable;
6 | import androidx.recyclerview.widget.LinearSmoothScroller;
7 | import androidx.recyclerview.widget.RecyclerView;
8 |
9 | /**
10 | * Helper class for LayoutManager to calculate distance
11 | *
12 | * @see LinearSmoothScroller
13 | */
14 | public class Rangefinder {
15 | private final RecyclerView.LayoutManager mLayoutManager;
16 |
17 | public Rangefinder(RecyclerView.LayoutManager layoutManager) {
18 | mLayoutManager = layoutManager;
19 | }
20 |
21 | @Nullable
22 | public RecyclerView.LayoutManager getLayoutManager() {
23 | return mLayoutManager;
24 | }
25 |
26 | /**
27 | * Calculates the vertical scroll amount necessary to make the given view fully visible
28 | * inside the RecyclerView.
29 | *
30 | * @param view The view which we want to make fully visible
31 | * @param snapPreference The edge which the view should snap to when entering the visible
32 | * area. One of {@link SnapPreference#SNAP_TO_START}, {@link SnapPreference#SNAP_TO_END} or
33 | * {@link SnapPreference#SNAP_TO_ANY}.
34 | * @return The vertical scroll amount necessary to make the view visible with the given
35 | * snap preference.
36 | */
37 | public int calculateDyToMakeVisible(View view, int snapPreference) {
38 | final RecyclerView.LayoutManager layoutManager = getLayoutManager();
39 | if (layoutManager == null || !layoutManager.canScrollVertically()) {
40 | return 0;
41 | }
42 | final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
43 | view.getLayoutParams();
44 | final int top = layoutManager.getDecoratedTop(view) - params.topMargin;
45 | final int bottom = layoutManager.getDecoratedBottom(view) + params.bottomMargin;
46 | final int start = layoutManager.getPaddingTop();
47 | final int end = layoutManager.getHeight() - layoutManager.getPaddingBottom();
48 | return calculateDtToFit(top, bottom, start, end, snapPreference);
49 | }
50 |
51 | /**
52 | * Calculates the horizontal scroll amount necessary to make the given view fully visible
53 | * inside the RecyclerView.
54 | *
55 | * @param view The view which we want to make fully visible
56 | * @param snapPreference The edge which the view should snap to when entering the visible
57 | * area. One of {@link SnapPreference#SNAP_TO_START}, {@link SnapPreference#SNAP_TO_END} or
58 | * {@link SnapPreference#SNAP_TO_END}
59 | * @return The vertical scroll amount necessary to make the view visible with the given
60 | * snap preference.
61 | */
62 | public int calculateDxToMakeVisible(View view, int snapPreference) {
63 | final RecyclerView.LayoutManager layoutManager = getLayoutManager();
64 | if (layoutManager == null || !layoutManager.canScrollHorizontally()) {
65 | return 0;
66 | }
67 | final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
68 | view.getLayoutParams();
69 | final int left = layoutManager.getDecoratedLeft(view) - params.leftMargin;
70 | final int right = layoutManager.getDecoratedRight(view) + params.rightMargin;
71 | final int start = layoutManager.getPaddingLeft();
72 | final int end = layoutManager.getWidth() - layoutManager.getPaddingRight();
73 | return calculateDtToFit(left, right, start, end, snapPreference);
74 | }
75 |
76 | /**
77 | * Helper method for {@link #calculateDxToMakeVisible(android.view.View, int)} and
78 | * {@link #calculateDyToMakeVisible(android.view.View, int)}
79 | */
80 | public int calculateDtToFit(int viewStart, int viewEnd, int boxStart, int boxEnd,
81 | @SnapPreference int snapPreference) {
82 | switch (snapPreference) {
83 | case SnapPreference.SNAP_TO_START:
84 | return boxStart - viewStart;
85 | case SnapPreference.SNAP_TO_END:
86 | return boxEnd - viewEnd;
87 | case SnapPreference.SNAP_TO_ANY:
88 | final int dtStart = boxStart - viewStart;
89 | if (dtStart > 0) {
90 | return dtStart;
91 | }
92 | final int dtEnd = boxEnd - viewEnd;
93 | if (dtEnd < 0) {
94 | return dtEnd;
95 | }
96 | break;
97 | case SnapPreference.SNAP_TO_CENTER:
98 | return (boxStart + (boxEnd - boxStart) / 2) - (viewStart + (viewEnd - viewStart) / 2);
99 | }
100 | return 0;
101 | }
102 | }
103 |
--------------------------------------------------------------------------------
/app/src/main/java/com/example/myapplication/ImmediateIndexScroller.java:
--------------------------------------------------------------------------------
1 | package com.example.myapplication;
2 |
3 | import android.view.View;
4 |
5 | import androidx.annotation.NonNull;
6 | import androidx.recyclerview.widget.RecyclerView;
7 |
8 | import java.util.Objects;
9 |
10 | public class ImmediateIndexScroller implements IndexScroller {
11 | private final RecyclerView mRecyclerView;
12 |
13 | public ImmediateIndexScroller(@NonNull RecyclerView recyclerView) {
14 | mRecyclerView = recyclerView;
15 | }
16 |
17 | @Override
18 | public void scrollToPosition(int position) {
19 | scrollToPosition(position, SnapPreference.SNAP_TO_ANY);
20 | }
21 |
22 | @Override
23 | public void scrollToPosition(int position, @SnapPreference int snapPreference) {
24 | RecyclerView recyclerView = mRecyclerView;
25 | RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
26 | if (layoutManager == null || position < 0) {
27 | return;
28 | }
29 | ImmediateScroller scroller = createScroller(recyclerView, snapPreference);
30 | scroller.start(position);
31 | }
32 |
33 | @NonNull
34 | protected ImmediateScroller createScroller(@NonNull RecyclerView recyclerView, @SnapPreference int snapPreference) {
35 | return new ImmediateScroller(recyclerView, snapPreference);
36 | }
37 |
38 | public static class ImmediateScroller {
39 | public final RecyclerView recyclerView;
40 | private final int mVerticalSnapPreference;
41 | private final int mHorizontalSnapPreference;
42 | private boolean mRunning;
43 | private int mTargetPosition = RecyclerView.NO_POSITION;
44 | private Runnable mScrollRunnable;
45 |
46 | public ImmediateScroller(@NonNull RecyclerView recyclerView, @SnapPreference int snapPreference) {
47 | this(recyclerView, snapPreference, snapPreference);
48 | }
49 |
50 | public ImmediateScroller(@NonNull RecyclerView recyclerView, @SnapPreference int verticalSnapPreference, @SnapPreference int horizontalSnapPreference) {
51 | this.recyclerView = recyclerView;
52 | mVerticalSnapPreference = verticalSnapPreference;
53 | mHorizontalSnapPreference = horizontalSnapPreference;
54 | }
55 |
56 | public void start(int position) {
57 | ImmediateScroller scroller = getScroller();
58 | if (scroller != null) {// stop previous scroller
59 | scroller.stop();
60 | }
61 | if (position == RecyclerView.NO_POSITION) {
62 | return;
63 | }
64 | mRunning = true;
65 | mTargetPosition = position;
66 | setScroller(this);
67 | recyclerView.scrollToPosition(position);
68 | recyclerView.post(mScrollRunnable = new Runnable() {
69 | @Override
70 | public void run() {
71 | mScrollRunnable = null;
72 | if (mRunning && mTargetPosition != RecyclerView.NO_POSITION) {
73 | View targetView = findViewByPosition(mTargetPosition);
74 | if (targetView != null) {
75 | onTargetFound(targetView);
76 | }
77 | }
78 | stop();
79 | }
80 | });
81 | }
82 |
83 | private int getTagKey() {
84 | return Objects.hash(recyclerView, ImmediateScroller.class);
85 | }
86 |
87 | private ImmediateScroller getScroller() {
88 | Object tag = recyclerView.getTag(getTagKey());
89 | return tag instanceof ImmediateScroller ? (ImmediateScroller) tag : null;
90 | }
91 |
92 | private void setScroller(ImmediateScroller scroller) {
93 | recyclerView.setTag(getTagKey(), scroller);
94 | }
95 |
96 | public void stop() {
97 | if (!mRunning) {
98 | return;
99 | }
100 | mRunning = false;
101 | mTargetPosition = RecyclerView.NO_POSITION;
102 | setScroller(null);
103 | if (mScrollRunnable != null) {
104 | recyclerView.removeCallbacks(mScrollRunnable);
105 | mScrollRunnable = null;
106 | }
107 | }
108 |
109 | protected View findViewByPosition(int position) {
110 | RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
111 | return layoutManager != null ? layoutManager.findViewByPosition(position) : null;
112 | }
113 |
114 | protected void onTargetFound(@NonNull View targetView) {
115 | Rangefinder rangefinder = new Rangefinder(recyclerView.getLayoutManager());
116 | final int dx = rangefinder.calculateDxToMakeVisible(targetView, getHorizontalSnapPreference());
117 | final int dy = rangefinder.calculateDyToMakeVisible(targetView, getVerticalSnapPreference());
118 | if (dx != 0 || dy != 0) {
119 | recyclerView.scrollBy(-dx, -dy);
120 | }
121 | }
122 |
123 | public int getHorizontalSnapPreference() {
124 | return mHorizontalSnapPreference;
125 | }
126 |
127 | public int getVerticalSnapPreference() {
128 | return mVerticalSnapPreference;
129 | }
130 | }
131 | }
132 |
--------------------------------------------------------------------------------
/app/src/main/res/drawable/ic_launcher_background.xml:
--------------------------------------------------------------------------------
1 |
2 |
7 |
10 |
15 |
20 |
25 |
30 |
35 |
40 |
45 |
50 |
55 |
60 |
65 |
70 |
75 |
80 |
85 |
90 |
95 |
100 |
105 |
110 |
115 |
120 |
125 |
130 |
135 |
140 |
145 |
150 |
155 |
160 |
165 |
170 |
171 |
--------------------------------------------------------------------------------
/app/src/main/java/com/example/myapplication/MainActivity.java:
--------------------------------------------------------------------------------
1 | package com.example.myapplication;
2 |
3 | import android.content.Context;
4 | import android.os.Bundle;
5 | import android.util.TypedValue;
6 | import android.view.Gravity;
7 | import android.view.View;
8 | import android.view.ViewGroup;
9 | import android.widget.EditText;
10 | import android.widget.RadioGroup;
11 | import android.widget.TextView;
12 |
13 | import androidx.annotation.NonNull;
14 | import androidx.appcompat.app.AppCompatActivity;
15 | import androidx.recyclerview.widget.DividerItemDecoration;
16 | import androidx.recyclerview.widget.LinearLayoutManager;
17 | import androidx.recyclerview.widget.LinearSmoothScroller;
18 | import androidx.recyclerview.widget.RecyclerView;
19 |
20 | public class MainActivity extends AppCompatActivity {
21 | private RecyclerView mRecyclerView;
22 | private EditText mEditText;
23 | private RadioGroup mScrollerGroup;
24 | private RadioGroup mPreferenceGroup;
25 |
26 | @Override
27 | protected void onCreate(Bundle savedInstanceState) {
28 | super.onCreate(savedInstanceState);
29 | setContentView(R.layout.activity_main);
30 |
31 | RecyclerView recyclerView = mRecyclerView = findViewById(R.id.recycler_view);
32 | LinearLayoutManager layoutManager = new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
33 | recyclerView.setLayoutManager(layoutManager);
34 | recyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.HORIZONTAL));
35 | SimpleAdapter adapter = new SimpleAdapter(500);
36 | recyclerView.setAdapter(adapter);
37 |
38 | mEditText = findViewById(R.id.edit_text);
39 | mEditText.setText("100");
40 |
41 | mScrollerGroup = findViewById(R.id.radio_group_scroller);
42 | mScrollerGroup.check(R.id.radio_button_smooth);
43 |
44 | mPreferenceGroup = findViewById(R.id.radio_group_align);
45 | mPreferenceGroup.check(R.id.radio_button_any);
46 |
47 | findViewById(R.id.btn_jump).setOnClickListener(new View.OnClickListener() {
48 | @Override
49 | public void onClick(View v) {
50 | onJump();
51 | // testJump();
52 | }
53 | });
54 | }
55 |
56 | private void onJump() {
57 | boolean useSmoothScroller = true;
58 | if (mScrollerGroup.getCheckedRadioButtonId() == R.id.radio_button_immediate) {
59 | useSmoothScroller = false;
60 | }
61 |
62 | int preference = SnapPreference.SNAP_TO_ANY;
63 | int preferenceId = mPreferenceGroup.getCheckedRadioButtonId();
64 | if (preferenceId == R.id.radio_button_start) {
65 | preference = SnapPreference.SNAP_TO_START;
66 | } else if (preferenceId == R.id.radio_button_end) {
67 | preference = SnapPreference.SNAP_TO_END;
68 | } else if (preferenceId == R.id.radio_button_center) {
69 | preference = SnapPreference.SNAP_TO_CENTER;
70 | }
71 |
72 | int position = Integer.parseInt(mEditText.getText().toString());
73 |
74 | IndexScroller indexScroller = useSmoothScroller
75 | ? new SmoothIndexScroller(mRecyclerView)
76 | : new ImmediateIndexScroller(mRecyclerView);
77 | indexScroller.scrollToPosition(position, preference);
78 | }
79 |
80 | private void testJump() {
81 | boolean useSmoothScroller = true;
82 | if (mScrollerGroup.getCheckedRadioButtonId() == R.id.radio_button_immediate) {
83 | useSmoothScroller = false;
84 | }
85 |
86 | int preference = SnapPreference.SNAP_TO_ANY;
87 | int preferenceId = mPreferenceGroup.getCheckedRadioButtonId();
88 | if (preferenceId == R.id.radio_button_start) {
89 | preference = SnapPreference.SNAP_TO_START;
90 | } else if (preferenceId == R.id.radio_button_end) {
91 | preference = SnapPreference.SNAP_TO_END;
92 | } else if (preferenceId == R.id.radio_button_center) {
93 | preference = SnapPreference.SNAP_TO_CENTER;
94 | }
95 |
96 | int position = Integer.parseInt(mEditText.getText().toString());
97 |
98 | if (useSmoothScroller) {
99 | testSmoothScroll(position, preference);
100 | } else {
101 | testScroll(position, preference);
102 | }
103 | }
104 |
105 | private void testScroll(int targetPosition, int preference) {
106 | RecyclerView recyclerView = mRecyclerView;
107 | RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
108 | recyclerView.scrollToPosition(targetPosition);
109 | recyclerView.post(new Runnable() {
110 | @Override
111 | public void run() {
112 | View targetView = layoutManager.findViewByPosition(targetPosition);
113 | if (targetView != null) {
114 | Rangefinder rangefinder = new Rangefinder(layoutManager);
115 | final int dx = rangefinder.calculateDxToMakeVisible(targetView, preference);
116 | final int dy = rangefinder.calculateDyToMakeVisible(targetView, preference);
117 | if (dx != 0 || dy != 0) {
118 | recyclerView.scrollBy(-dx, -dy);
119 | }
120 | }
121 | }
122 | });
123 | }
124 |
125 | private void testSmoothScroll(int targetPosition, int preference) {
126 | RecyclerView.LayoutManager layoutManager = mRecyclerView.getLayoutManager();
127 | LinearSmoothScroller smoothScroller = new LinearSmoothScroller(this) {
128 | @Override
129 | protected int getHorizontalSnapPreference() {
130 | return preference;
131 | }
132 |
133 | @Override
134 | protected int getVerticalSnapPreference() {
135 | return preference;
136 | }
137 |
138 | @Override
139 | public int calculateDtToFit(int viewStart, int viewEnd, int boxStart, int boxEnd, int snapPreference) {
140 | if (snapPreference == SnapPreference.SNAP_TO_CENTER) {
141 | return (boxStart + (boxEnd - boxStart) / 2) - (viewStart + (viewEnd - viewStart) / 2);
142 | }
143 | return super.calculateDtToFit(viewStart, viewEnd, boxStart, boxEnd, snapPreference);
144 | }
145 | };
146 | smoothScroller.setTargetPosition(targetPosition);
147 | layoutManager.startSmoothScroll(smoothScroller);
148 | }
149 |
150 | public static class SimpleAdapter extends RecyclerView.Adapter {
151 | private final int mCount;
152 |
153 | public SimpleAdapter(int count) {
154 | mCount = count;
155 | }
156 |
157 | @NonNull
158 | @Override
159 | public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
160 | return ViewHolder.create(parent.getContext());
161 | }
162 |
163 | @Override
164 | public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
165 | holder.mTextView.setText(String.valueOf(position));
166 | }
167 |
168 | @Override
169 | public int getItemCount() {
170 | return mCount;
171 | }
172 |
173 | public static class ViewHolder extends RecyclerView.ViewHolder {
174 | private final TextView mTextView;
175 |
176 | public ViewHolder(@NonNull TextView itemView) {
177 | super(itemView);
178 | mTextView = itemView;
179 | }
180 |
181 | public static ViewHolder create(Context context) {
182 | TextView textView = new TextView(context);
183 | textView.setGravity(Gravity.CENTER);
184 | int dp40 = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 40,
185 | context.getResources().getDisplayMetrics());
186 | textView.setLayoutParams(new RecyclerView.LayoutParams(dp40, RecyclerView.LayoutParams.MATCH_PARENT));
187 | return new ViewHolder(textView);
188 | }
189 | }
190 | }
191 | }
--------------------------------------------------------------------------------
/gradlew:
--------------------------------------------------------------------------------
1 | #!/bin/sh
2 |
3 | #
4 | # Copyright © 2015-2021 the original authors.
5 | #
6 | # Licensed under the Apache License, Version 2.0 (the "License");
7 | # you may not use this file except in compliance with the License.
8 | # You may obtain a copy of the License at
9 | #
10 | # https://www.apache.org/licenses/LICENSE-2.0
11 | #
12 | # Unless required by applicable law or agreed to in writing, software
13 | # distributed under the License is distributed on an "AS IS" BASIS,
14 | # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 | # See the License for the specific language governing permissions and
16 | # limitations under the License.
17 | #
18 |
19 | ##############################################################################
20 | #
21 | # Gradle start up script for POSIX generated by Gradle.
22 | #
23 | # Important for running:
24 | #
25 | # (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
26 | # noncompliant, but you have some other compliant shell such as ksh or
27 | # bash, then to run this script, type that shell name before the whole
28 | # command line, like:
29 | #
30 | # ksh Gradle
31 | #
32 | # Busybox and similar reduced shells will NOT work, because this script
33 | # requires all of these POSIX shell features:
34 | # * functions;
35 | # * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
36 | # «${var#prefix}», «${var%suffix}», and «$( cmd )»;
37 | # * compound commands having a testable exit status, especially «case»;
38 | # * various built-in commands including «command», «set», and «ulimit».
39 | #
40 | # Important for patching:
41 | #
42 | # (2) This script targets any POSIX shell, so it avoids extensions provided
43 | # by Bash, Ksh, etc; in particular arrays are avoided.
44 | #
45 | # The "traditional" practice of packing multiple parameters into a
46 | # space-separated string is a well documented source of bugs and security
47 | # problems, so this is (mostly) avoided, by progressively accumulating
48 | # options in "$@", and eventually passing that to Java.
49 | #
50 | # Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
51 | # and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
52 | # see the in-line comments for details.
53 | #
54 | # There are tweaks for specific operating systems such as AIX, CygWin,
55 | # Darwin, MinGW, and NonStop.
56 | #
57 | # (3) This script is generated from the Groovy template
58 | # https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
59 | # within the Gradle project.
60 | #
61 | # You can find Gradle at https://github.com/gradle/gradle/.
62 | #
63 | ##############################################################################
64 |
65 | # Attempt to set APP_HOME
66 |
67 | # Resolve links: $0 may be a link
68 | app_path=$0
69 |
70 | # Need this for daisy-chained symlinks.
71 | while
72 | APP_HOME=${app_path%"${app_path##*/}"} # leaves a trailing /; empty if no leading path
73 | [ -h "$app_path" ]
74 | do
75 | ls=$( ls -ld "$app_path" )
76 | link=${ls#*' -> '}
77 | case $link in #(
78 | /*) app_path=$link ;; #(
79 | *) app_path=$APP_HOME$link ;;
80 | esac
81 | done
82 |
83 | APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
84 |
85 | APP_NAME="Gradle"
86 | APP_BASE_NAME=${0##*/}
87 |
88 | # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
89 | DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
90 |
91 | # Use the maximum available, or set MAX_FD != -1 to use that value.
92 | MAX_FD=maximum
93 |
94 | warn () {
95 | echo "$*"
96 | } >&2
97 |
98 | die () {
99 | echo
100 | echo "$*"
101 | echo
102 | exit 1
103 | } >&2
104 |
105 | # OS specific support (must be 'true' or 'false').
106 | cygwin=false
107 | msys=false
108 | darwin=false
109 | nonstop=false
110 | case "$( uname )" in #(
111 | CYGWIN* ) cygwin=true ;; #(
112 | Darwin* ) darwin=true ;; #(
113 | MSYS* | MINGW* ) msys=true ;; #(
114 | NONSTOP* ) nonstop=true ;;
115 | esac
116 |
117 | CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
118 |
119 |
120 | # Determine the Java command to use to start the JVM.
121 | if [ -n "$JAVA_HOME" ] ; then
122 | if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
123 | # IBM's JDK on AIX uses strange locations for the executables
124 | JAVACMD=$JAVA_HOME/jre/sh/java
125 | else
126 | JAVACMD=$JAVA_HOME/bin/java
127 | fi
128 | if [ ! -x "$JAVACMD" ] ; then
129 | die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
130 |
131 | Please set the JAVA_HOME variable in your environment to match the
132 | location of your Java installation."
133 | fi
134 | else
135 | JAVACMD=java
136 | which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
137 |
138 | Please set the JAVA_HOME variable in your environment to match the
139 | location of your Java installation."
140 | fi
141 |
142 | # Increase the maximum file descriptors if we can.
143 | if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
144 | case $MAX_FD in #(
145 | max*)
146 | MAX_FD=$( ulimit -H -n ) ||
147 | warn "Could not query maximum file descriptor limit"
148 | esac
149 | case $MAX_FD in #(
150 | '' | soft) :;; #(
151 | *)
152 | ulimit -n "$MAX_FD" ||
153 | warn "Could not set maximum file descriptor limit to $MAX_FD"
154 | esac
155 | fi
156 |
157 | # Collect all arguments for the java command, stacking in reverse order:
158 | # * args from the command line
159 | # * the main class name
160 | # * -classpath
161 | # * -D...appname settings
162 | # * --module-path (only if needed)
163 | # * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
164 |
165 | # For Cygwin or MSYS, switch paths to Windows format before running java
166 | if "$cygwin" || "$msys" ; then
167 | APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
168 | CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
169 |
170 | JAVACMD=$( cygpath --unix "$JAVACMD" )
171 |
172 | # Now convert the arguments - kludge to limit ourselves to /bin/sh
173 | for arg do
174 | if
175 | case $arg in #(
176 | -*) false ;; # don't mess with options #(
177 | /?*) t=${arg#/} t=/${t%%/*} # looks like a POSIX filepath
178 | [ -e "$t" ] ;; #(
179 | *) false ;;
180 | esac
181 | then
182 | arg=$( cygpath --path --ignore --mixed "$arg" )
183 | fi
184 | # Roll the args list around exactly as many times as the number of
185 | # args, so each arg winds up back in the position where it started, but
186 | # possibly modified.
187 | #
188 | # NB: a `for` loop captures its iteration list before it begins, so
189 | # changing the positional parameters here affects neither the number of
190 | # iterations, nor the values presented in `arg`.
191 | shift # remove old arg
192 | set -- "$@" "$arg" # push replacement arg
193 | done
194 | fi
195 |
196 | # Collect all arguments for the java command;
197 | # * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
198 | # shell script including quotes and variable substitutions, so put them in
199 | # double quotes to make sure that they get re-expanded; and
200 | # * put everything else in single quotes, so that it's not re-expanded.
201 |
202 | set -- \
203 | "-Dorg.gradle.appname=$APP_BASE_NAME" \
204 | -classpath "$CLASSPATH" \
205 | org.gradle.wrapper.GradleWrapperMain \
206 | "$@"
207 |
208 | # Use "xargs" to parse quoted args.
209 | #
210 | # With -n1 it outputs one arg per line, with the quotes and backslashes removed.
211 | #
212 | # In Bash we could simply go:
213 | #
214 | # readarray ARGS < <( xargs -n1 <<<"$var" ) &&
215 | # set -- "${ARGS[@]}" "$@"
216 | #
217 | # but POSIX shell has neither arrays nor command substitution, so instead we
218 | # post-process each arg (as a line of input to sed) to backslash-escape any
219 | # character that might be a shell metacharacter, then use eval to reverse
220 | # that process (while maintaining the separation between arguments), and wrap
221 | # the whole thing up as a single "set" statement.
222 | #
223 | # This will of course break if any of these variables contains a newline or
224 | # an unmatched quote.
225 | #
226 |
227 | eval "set -- $(
228 | printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
229 | xargs -n1 |
230 | sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
231 | tr '\n' ' '
232 | )" '"$@"'
233 |
234 | exec "$JAVACMD" "$@"
235 |
--------------------------------------------------------------------------------