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。
image.png
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
- @android:color/transparent
- true
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
//R.anim.slide_right_out
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_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_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();
}