android 右滑返回的示例代码

类似于微信的右滑返回，在BaseActivity里利用dispatchTouchEvent（）拦截右滑动作，利用setTranslationX（）实现动画，在DecorView里添加View作为滑动时的左侧阴影。

渐进步骤：

设置activity背景透明
重写finish（）等方法设置activity的跳转动画
重写dispatchTouchEvent（）拦截所需要右滑动作
重写onTouchEvent（）给根布局设置偏移量
添加滑动时上层activity的左侧阴影
滑动时关联下层activity滑动

注意：步骤中的代码为了不关联到后面的步骤，会与最终的有点不同

背景透明

  <item name="android:windowBackground" @android:color/transparent</item 
  <item name="android:windowIsTranslucent" true</item

activity的跳转动画

根据项目需要，重写用到的startActivity(Intent intent)，startActivityForResult(Intent intent, int requestCode)，finish()等activity跳转和销毁方法

@Override
public void startActivity(Intent intent) {
  super.startActivity(intent);
  overridePendingTransition(R.anim.slide_right_in, 0);
}

@Override
public void startActivityForResult(Intent intent, int requestCode) {
  super.startActivityForResult(intent, requestCode);
  overridePendingTransition(R.anim.slide_right_in, 0);
}

@Override
public void finish() {
  super.finish();
  overridePendingTransition(0, R.anim.slide_right_out);
}

//R.anim.slide_right_in
<set xmlns:android="http://schemas.android.com/apk/res/android" 
 <translate
   android:duration="300"
   android:fromXDelta="100%"
   android:toXDelta="0"
   android:fromYDelta="0"
   android:toYDelta="0"/ 
</set 

//R.anim.slide_right_out
<set xmlns:android="http://schemas.android.com/apk/res/android" 
 <translate
   android:duration="300"
   android:fromXDelta="0"
   android:toXDelta="100%"
   android:fromYDelta="0"
   android:toYDelta="0" / 
</set

拦截右滑动作

所有的触摸事件通过activity.dispatchTouchEvent(MotionEvent ev)向view分发。手指在X轴方向右滑动50~100px时，判断是否为（产品经理要）右滑动作

手指落点为全屏幕，X方向滑动距离要比Y方向的大一些；
手指落点为左侧边，X方向滑动距离有一些就行

private float downX = 0;
private float downY = 0;
private boolean shouldIntercept = false;
private boolean hadJudge = false;

@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
  if (shouldIntercept) {
    return onTouchEvent(ev);
  }
  switch (ev.getAction()) {
    case MotionEvent.ACTION_DOWN: {
      downX = ev.getRawX();
      downY = ev.getRawY();
      hadJudge = false;
      break;
    }
    case MotionEvent.ACTION_MOVE: {
      if (hadJudge) break;
      if (ev.getRawX() == downX) break;
      if (ev.getRawX() < downX) {
        //左滑
        hadJudge = true;
        break;
      }
      if (ev.getRawX() - downX  =100){
        //超出判断距离
        hadJudge = true;
        break;
      }
      if (ev.getRawX() - downX   50) {
        //x轴右滑50~100px
        float rate = (ev.getRawX() - downX) / (Math.abs(ev.getRawY() - downY));
        if ((downX < 50 && rate   0.5f) || rate   2) {
          shouldIntercept = true;
        }
      }
      break;
    }
    case MotionEvent.ACTION_UP: {
      downX =0;
      downY = 0;
      shouldIntercept = false;
      hadJudge=false;
      break;
    }
  }
  //Activity的默认分发
  if (ev.getAction() == MotionEvent.ACTION_DOWN) {
    onUserInteraction();
  }
  if (getWindow().superDispatchTouchEvent(ev)) {
    return true;
  }
  return true;
}

根布局位移动画

根据手指滑动距离设置根布局偏移距离，用滑动距离和手指抬起时的速度判断是否返回

private View rootView = null;
private float lastX = -1;  
private VelocityTracker velocityTracker = null;
private int maxFlingVelocity;


@Override
public boolean onTouchEvent(MotionEvent event) {
  if (rootView == null) {
    ViewGroup rootGroup = (ViewGroup) (getWindow().getDecorView());
    rootView = rootGroup.getChildAt(0);
  }
  //测量手指抬起时的速度
  if (velocityTracker == null) {
    velocityTracker = VelocityTracker.obtain();
    maxFlingVelocity = ViewConfiguration.get(this).getScaledMaximumFlingVelocity();
  }
  velocityTracker.addMovement(event);


  switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN: {
      lastX = event.getRawX();
      break;
    }
    case MotionEvent.ACTION_MOVE: {
      if (lastX == -1) {
        lastX = event.getRawX();
        break;
      }
      //根据手指滑动距离设置根布局偏移距离
      rootView.setTranslationX(rootView.getTranslationX() + event.getRawX() - lastX);
      if (rootView.getTranslationX() < 0) rootView.setTranslationX(0);
      lastX = event.getRawX();
      break;
    }
    case MotionEvent.ACTION_UP: {
      //测量手指抬起时的速度
      velocityTracker.computeCurrentVelocity(1000, maxFlingVelocity);
      float velocityX = velocityTracker.getXVelocity();
      if (velocityTracker != null) {
        velocityTracker.recycle();
        velocityTracker = null;
      }

      //判断是否返回
      if (downX < 50 && velocityX   1000) {
        //手指在左侧边落下，返回
        onBack();
      } else if (velocityX   3600) {
        //手指快速滑动，返回
        onBack();
      } else if (rootView.getTranslationX()   ConvertUtil.getWidthInPx() * 0.3) {
        //滑动距离超过30%屏幕宽度，返回
        onBack();
      } else {
        //不返回，根布局偏移归零
        rootView.animate().translationX(0).setDuration(200).start();
      }
      
      lastX = -1;
      shouldIntercept = false;
      hadJudge=false;
      downX = 0;
      downY = 0;
      break;
    }
  }
  return super.onTouchEvent(event);
}

添加左侧阴影

Activity的最顶层View为DecorView，DecorView是一个FrameLayout，里面只有一个Linearlayout,Linearlayout包含着标题栏和自定义布局（setContentView）。上一步跟随手指滑动进行偏移的就是Linearlayout，现在要在DecorView里添加一个View，设置背景作为阴影，并跟随Linearlayout进行移动

private View shadowView = null;
@Override
public boolean onTouchEvent(MotionEvent event) {
  if (rootView == null) {
    //添加阴影
    
    ViewGroup rootGroup = (ViewGroup) (getWindow().getDecorView());

    shadowView = new View(this);
    rootGroup.addView(shadowView, 0);
    ViewGroup.LayoutParams params = shadowView.getLayoutParams();
    //阴影宽度
    params.width = (int) ((float) ConvertUtil.getWidthInPx() * 0.05f);
    params.height = ConvertUtil.getHeightInPx();
    shadowView.setLayoutParams(params);
    shadowView.setBackgroundResource(R.drawable.shadow_grey_h);
    shadowView.setTranslationX(params.width);

    rootView = rootGroup.getChildAt(1);
  }

  ...

  switch (event.getAction()) {
    ...
    case MotionEvent.ACTION_MOVE: {
      if (lastX == -1) {
        lastX = event.getRawX();
        break;
      }
      //根据手指滑动距离设置根布局偏移距离
      rootView.setTranslationX(rootView.getTranslationX() + event.getRawX() - lastX);
      if (rootView.getTranslationX() < 0) rootView.setTranslationX(0);
      //阴影跟随根布局移动
      shadowView.setTranslationX(-shadowView.getWidth()+rootView.getTranslationX());
      lastX = event.getRawX();
      break;
    }
    case MotionEvent.ACTION_UP: {
      ...
      } else {
        //不返回，根布局偏移归零
        rootView.animate().translationX(0).setDuration(200).start();
        //阴影偏移归零
        shadowView.animate().translationX(-shadowView.getWidth()).setDuration(200).start();
      }
      ...
    }
  }
  ...
}

关联下层activity滑动

保存所有的activity以获取下层activity
给下层activity添加退出和进入的动画
在上层activity滑动时调用下层滑动

获取下层activity

private static ArrayList<Activity  Activity_Stack = new ArrayList< ();
private BaseSwipeBackActivity lastActivity = null;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  maxFlingVelocity = ViewConfiguration.get(this).getScaledMaximumFlingVelocity();

  if (!Activity_Stack.contains(this)) Activity_Stack.add(this);
  if (Activity_Stack.size()  = 2) {
    Activity last = Activity_Stack.get(Activity_Stack.size() - 2);
    if (last instanceof BaseSwipeBackActivity) {
      lastActivity = (BaseSwipeBackActivity) last;
    }
  }
}

@Override
protected void onDestroy() {
  super.onDestroy();
  Activity_Stack.remove(this);
}

下层activity的退出、进入动画

private void lowerActivityExitAnim() {
  if (rootView == null) return;
  //只移动30%
  rootView.animate().translationX(-ConvertUtil.getWidthInPx() * 0.3f).setDuration(300).start();
}

private void lowerActivityEnterAnim(float upperTranslationX) {
  if (rootView == null) return;
  //保证滑动退出时，上下层时间同步
  float r = 1-upperTranslationX/ (float) ConvertUtil.getWidthInPx();
  rootView.animate().translationX(0).setDuration((long) (300f * r)).start();
}

在跳转时，调用下层activity的退出、进入动画

@Override
public void startActivity(Intent intent) {
  super.startActivity(intent);
  overridePendingTransition(R.anim.slide_right_in, 0);
  lowerActivityExitAnim();
}

@Override
public void startActivityForResult(Intent intent, int requestCode) {
  super.startActivityForResult(intent, requestCode);
  overridePendingTransition(R.anim.slide_right_in, 0);
  lowerActivityExitAnim();
}

@Override
public void finish() {
  super.finish();
  overridePendingTransition(0, R.anim.slide_right_out);
  if (lastActivity != null) lastActivity.lowerActivityEnterAnim(rootView.getTranslationX());
  Activity_Stack.remove(this);
}

上层activity滑动时关联下层滑动

@Override
public boolean onTouchEvent(MotionEvent event) {
  ...
  switch (event.getAction()) {
    ...
    case MotionEvent.ACTION_MOVE: {
      ...
      //根据手指滑动距离设置根布局偏移距离
      rootView.setTranslationX(rootView.getTranslationX() + event.getRawX() - lastX);
      if (rootView.getTranslationX() < 0) rootView.setTranslationX(0);
      //阴影跟随根布局移动
      shadowView.setTranslationX(-shadowView.getWidth() + rootView.getTranslationX());
      //下层activity跟随移动
      if (lastActivity != null && lastActivity.rootView != null)
        //-ConvertUtil.getWidthInPx() * 0.3f初始的偏移
        lastActivity.rootView.setTranslationX(-ConvertUtil.getWidthInPx() * 0.3f + rootView.getTranslationX() * 0.3f);
      ...
    }
    case MotionEvent.ACTION_UP: {
      ...
      } else {
        //不返回，根布局偏移归零
        rootView.animate().translationX(0).setDuration(200).start();
        //阴影偏移归零
        shadowView.animate().translationX(-shadowView.getWidth()).setDuration(200).start();
        //下层activity偏移复原
        if (lastActivity != null)
          lastActivity.lowerActivityExitAnim();
      }
      ...
    }
  }

  return super.onTouchEvent(event);
}

完整的

public abstract class BaseSwipeBackActivity extends AppCompatActivity {
private static ArrayList<Activity  Activity_Stack = new ArrayList< ();
private BaseSwipeBackActivity lastActivity = null;
private View rootView = null;
private View shadowView = null;
private float downX = 0;
private float downY = 0;
private boolean shouldIntercept = false;
private boolean hadJudge = false;
private float lastX = -1;
private VelocityTracker velocityTracker = null;
private int maxFlingVelocity;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
maxFlingVelocity = ViewConfiguration.get(this).getScaledMaximumFlingVelocity();
if (!Activity_Stack.contains(this)) Activity_Stack.add(this);
if (Activity_Stack.size()  = 2) {
Activity last = Activity_Stack.get(Activity_Stack.size() - 2);
if (last instanceof BaseSwipeBackActivity) {
lastActivity = (BaseSwipeBackActivity) last;
}
}
}
@Override
protected void onResume() {
initShadow();
super.onResume();
}
@Override
protected void onDestroy() {
super.onDestroy();
Activity_Stack.remove(this);
}
@Override
public void startActivity(Intent intent) {
super.startActivity(intent);
overridePendingTransition(R.anim.slide_right_in, 0);
lowerActivityExitAnim();
}
@Override
public void startActivityForResult(Intent intent, int requestCode) {
super.startActivityForResult(intent, requestCode);
overridePendingTransition(R.anim.slide_right_in, 0);
lowerActivityExitAnim();
}
@Override
public void finish() {
super.finish();
overridePendingTransition(0, R.anim.slide_right_out);
if (lastActivity != null) lastActivity.lowerActivityEnterAnim(rootView.getTranslationX());
Activity_Stack.remove(this);
}
private void initShadow() {
if (shadowView == null) {
ViewGroup rootGroup = (ViewGroup) (getWindow().getDecorView());
shadowView = new View(this);
rootGroup.addView(shadowView, 0);
ViewGroup.LayoutParams params = shadowView.getLayoutParams();
//阴影宽度
params.width = (int) ((float) ConvertUtil.getWidthInPx() * 0.05f);
params.height = ConvertUtil.getHeightInPx();
shadowView.setLayoutParams(params);
//渐变背景作为阴影
shadowView.setBackgroundResource(R.drawable.shadow_grey_h);
shadowView.setTranslationX(-params.width);
rootView = rootGroup.getChildAt(1);
}
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if (shouldIntercept) {
return onTouchEvent(ev);
}
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN: {
downX = ev.getRawX();
downY = ev.getRawY();
hadJudge = false;
break;
}
case MotionEvent.ACTION_MOVE: {
if (hadJudge) break;
if (ev.getRawX() == downX) break;
if (ev.getRawX() < downX) {
//左滑
hadJudge = true;
break;
}
if (ev.getRawX() - downX  = 100) {
//超出判断距离
hadJudge = true;
break;
}
if (ev.getRawX() - downX   50) {
//x轴右滑50~100px
float rate = (ev.getRawX() - downX) / (Math.abs(ev.getRawY() - downY));
if ((downX < 50 && rate   0.5f) || rate   2) {
shouldIntercept = true;
}
}
break;
}
case MotionEvent.ACTION_UP: {
downX = 0;
downY = 0;
shouldIntercept = false;
hadJudge = false;
break;
}
}
//Activity的默认分发
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
onUserInteraction();
}
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
return true;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
initShadow();
//测量手指抬起时的速度
if (velocityTracker == null) {
velocityTracker = VelocityTracker.obtain();
maxFlingVelocity = ViewConfiguration.get(this).getScaledMaximumFlingVelocity();
}
velocityTracker.addMovement(event);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN: {
lastX = event.getRawX();
break;
}
case MotionEvent.ACTION_MOVE: {
if (lastX == -1) {
lastX = event.getRawX();
break;
}
//根据手指滑动距离设置根布局偏移距离
rootView.setTranslationX(rootView.getTranslationX() + event.getRawX() - lastX);
if (rootView.getTranslationX() < 0) rootView.setTranslationX(0);
//阴影跟随根布局移动
shadowView.setTranslationX(-shadowView.getWidth() + rootView.getTranslationX());
//下层activity跟随移动
if (lastActivity != null && lastActivity.rootView != null)
lastActivity.rootView.setTranslationX(-ConvertUtil.getWidthInPx() * 0.3f + rootView.getTranslationX() * 0.3f);
lastX = event.getRawX();
break;
}
case MotionEvent.ACTION_UP: {
//测量手指抬起时的速度
velocityTracker.computeCurrentVelocity(1000, maxFlingVelocity);
float velocityX = velocityTracker.getXVelocity();
if (velocityTracker != null) {
velocityTracker.recycle();
velocityTracker = null;
}
//判断是否返回
if (downX < 50 && velocityX   1000) {
//手指在左侧边落下，返回
onBack();
} else if (velocityX   3600) {
//手指快速滑动，返回
onBack();
} else if (rootView.getTranslationX()   ConvertUtil.getWidthInPx() * 0.3) {
//滑动距离超过30%屏幕宽度，返回
onBack();
} else {
//不返回，根布局偏移归零
rootView.animate().translationX(0).setDuration(200).start();
//阴影偏移归零
shadowView.animate().translationX(-shadowView.getWidth()).setDuration(200).start();
//下层activity偏移复原
if (lastActivity != null) lastActivity.lowerActivityExitAnim();
}
lastX = -1;
shouldIntercept = false;
hadJudge = false;
downX = 0;
downY = 0;
break;
}
}
return super.onTouchEvent(event);
}
private void lowerActivityExitAnim() {
if (rootView == null) return;
rootView.animate().translationX(-ConvertUtil.getWidthInPx() * 0.3f).setDuration(300).start();
}
private void lowerActivityEnterAnim(float upperTranslationX) {
if (rootView == null) return;
float r = 1-upperTranslationX/ (float) ConvertUtil.getWidthInPx();
rootView.animate().translationX(0).setDuration(r == 0.0f ? 10 : (long) (300f * r)).start();
}
//退出
abstract public void onBack();
}

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