实现Activity滑动退出
很多应用在二级详情页面加入了滑动退出activity的效果，很方便，心血来潮，想着自己也来实现这个效果，就当做练手吧。
实现View的滑动有很多种方法，如自己在onTouchEvent中处理触摸事件，然后滚动View到相应位置，也可以用google V4包为我们提供的ViewDragHelper来处理触摸事件，我们这里选择后者，因为滑动退出操作都是在屏幕的边缘时触发，而ViewDragHelper刚好提供了想要的实现，可以说利用ViewDragHelper来实现我们的需求非常简单。
先定义一个ViewGroup，并做一些必要的变量声明
BaseSwipeLayout
public class BaseSwipeLayout extends FrameLayout{
private View mDragView;
private ViewDragHelper mViewDragHelper;
private Point mAutoBackOrignalPoint = new Point();
private Point mCurArrivePoint = new Point();
private int mCurEdgeFlag = ViewDragHelper.EDGE_LEFT;
private int mSwipeEdge = ViewDragHelper.EDGE_LEFT;
public BaseSwipeLayout(Context context) {
this(context, null);
}
public BaseSwipeLayout(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public BaseSwipeLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
}
既然使用ViewDragHelper，我们把触摸事件交给ViewDragHelper处理，ViewDragHelper不熟悉的同学，相关知识，网上一大堆，自行查看
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return mViewDragHelper.shouldInterceptTouchEvent(ev);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
mViewDragHelper.processTouchEvent(event);
return true;
}
下面对ViewDragHelper的配置，比较简单，大家看代码吧。
private void init() {
mViewDragHelper = ViewDragHelper.create(this, 1.0f, new ViewDragHelper.Callback() {
@Override
public boolean tryCaptureView(View child, int pointerId) {
return false;
}
@Override
public int clampViewPositionHorizontal(View child, int left, int dx) {
mCurArrivePoint.x = left;
//允许左右触发滑动，否则return 0
if (mCurEdgeFlag != ViewDragHelper.EDGE_BOTTOM) {
return left;
}else return 0;
}
@Override
public int clampViewPositionVertical(View child, int top, int dy) {
mCurArrivePoint.y = top;
//允许底部触发滑动，否则return 0
if (mCurEdgeFlag == ViewDragHelper.EDGE_BOTTOM) {
return top;
}else return 0;
}
@Override
public void onViewReleased(View releasedChild, float xvel, float yvel) {
super.onViewReleased(releasedChild, xvel, yvel);
switch (mCurEdgeFlag) {
case ViewDragHelper.EDGE_LEFT:
//水平滑动超过一半，触发结束
if (mCurArrivePoint.x > getWidth()/2) {
mViewDragHelper.settleCapturedViewAt(getWidth(), mAutoBackOrignalPoint.y);
}else {
mViewDragHelper.settleCapturedViewAt(mAutoBackOrignalPoint.x, mAutoBackOrignalPoint.y);
}
break;
case ViewDragHelper.EDGE_RIGHT:
//水平滑动超过一半，触发结束
if (mCurArrivePoint.x < -getWidth()/2) {
mViewDragHelper.settleCapturedViewAt(-getWidth(), mAutoBackOrignalPoint.y);
}else {
mViewDragHelper.settleCapturedViewAt(mAutoBackOrignalPoint.x, mAutoBackOrignalPoint.y);
}
break;
case ViewDragHelper.EDGE_BOTTOM:
//垂直滑动超过一半，触发结束
if (mCurArrivePoint.y < -getHeight()/2) {
mViewDragHelper.settleCapturedViewAt(mAutoBackOrignalPoint.x, -getHeight());
}else {
mViewDragHelper.settleCapturedViewAt(mAutoBackOrignalPoint.x, mAutoBackOrignalPoint.y);
}
break;
}
mCurArrivePoint.x = 0;
mCurArrivePoint.y = 0;
invalidate();
}
@Override
public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
super.onViewPositionChanged(changedView, left, top, dx, dy);
switch (mCurEdgeFlag) {
case ViewDragHelper.EDGE_LEFT:
if (left >= getWidth()) {
if (mFinishScroll != null) {
mFinishScroll.complete();
}
}
break;
case ViewDragHelper.EDGE_RIGHT:
if (left <= -getWidth()) {
if (mFinishScroll != null) {
mFinishScroll.complete();
}
}
break;
case ViewDragHelper.EDGE_BOTTOM:
if (top <= -getHeight()) {
if (mFinishScroll != null) {
mFinishScroll.complete();
}
}
break;
}
}
@Override
public void onEdgeDragStarted(int edgeFlags, int pointerId) {
mCurEdgeFlag = edgeFlags;
if (mDragView == null) mDragView = getChildAt(0);
mViewDragHelper.captureChildView(mDragView, pointerId);
}
});
mViewDragHelper.setEdgeTrackingEnabled(ViewDragHelper.EDGE_LEFT);
}
这里还有个步骤不要忘了，手指离开屏幕或者滑动超过屏幕的时候，我们触发了ViewGroup自行完全滚动出屏幕的调用，所以我们需要在computeScroll中做检查，如果滚动没有结束，刷新View，继续滚动。
@Override
public void computeScroll() {
if (mViewDragHelper.continueSettling(true)) {
invalidate();
}
}
这样我们自定义的BaseSwipeLayout打造完毕，我们把它设为activity的根布局测试一下
<?xml version="1.0" encoding="utf-8"?>
<com.aliouswang.swipeback.widget.BaseSwipeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:id="@+id/swipe_layout"
android:layout_height="match_parent">
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:text="Swipe Back Demo"
android:gravity="center"
android:textColor="@android:color/white"
android:background="@android:color/holo_red_light"
android:layout_width="match_parent"
android:layout_height="100dp" />
<TextView
android:text="Swipe Back Demo"
android:gravity="center"
android:textColor="@android:color/white"
android:background="@android:color/holo_blue_light"
android:layout_width="match_parent"
android:layout_height="100dp" />
<TextView
android:text="Swipe Back Demo"
android:gravity="center"
android:textColor="@android:color/white"
android:background="@android:color/holo_green_light"
android:layout_width="match_parent"
android:layout_height="100dp" />
<TextView
android:text="Swipe Back Demo"
android:gravity="center"
android:textColor="@android:color/white"
android:background="@android:color/holo_purple"
android:layout_width="match_parent"
android:layout_height="100dp" />
<TextView
android:text="Swipe Back Demo"
android:gravity="center"
android:textColor="@android:color/white"
android:background="@android:color/holo_green_dark"
android:layout_width="match_parent"
android:layout_height="100dp" />
<TextView
android:text="Swipe Back Demo"
android:gravity="center"
android:textColor="@android:color/white"
android:background="@android:color/holo_red_dark"
android:layout_width="match_parent"
android:layout_height="100dp" />
<TextView
android:text="Swipe Back Demo"
android:gravity="center"
android:textColor="@android:color/white"
android:background="@android:color/holo_blue_dark"
android:layout_width="match_parent"
android:layout_height="100dp" />
<TextView
android:text="Swipe Back Demo"
android:gravity="center"
android:textColor="@android:color/white"
android:background="@android:color/holo_orange_dark"
android:layout_width="match_parent"
android:layout_height="100dp" />
</LinearLayout>
</ScrollView>
</com.aliouswang.swipeback.widget.BaseSwipeLayout>
当然，我们已经实现了整个功能，但是有一点很不爽的是，我们必须将BaseSwipeLayout作为布局的根，这样实现还不够优雅，我们能不能不改变我们原有的布局文件，却依然能加入滑动退出功能。
这里我们要介绍一个DecorView，它是Window的最顶层View，它含有一个子LinearLayout，代表整个Window，包括通知栏，状态栏，内容显示区域，所以我们activity页面是DecorView的子View的子View，那么我们能不能直接给DecorView的子View添加到我们的BaseSwipeLayout，再将BaseSwipeLayout添加到DecorView，当然是可以的，而且这种方式，我们不需要改变原来的布局文件，更加优雅。
我们定义一个SwipeHelper类，辅助我们进行BaseSwipeLayout插入操作。
public class SwipeHelper {
private Activity mActivity;
private BaseSwipeLayout mBaseSwipeLayout;
public SwipeHelper(Activity activity) {
this.mActivity = activity;
}
public void onActivityCreate() {
mBaseSwipeLayout = (BaseSwipeLayout) LayoutInflater.from(mActivity)
.inflate(R.layout.swipe_layout, null);
mBaseSwipeLayout.setOnFinishScroll(new BaseSwipeLayout.OnFinishScroll() {
@Override
public void complete() {
mActivity.finish();
}
});
}
public void onPostCreate() {
mBaseSwipeLayout.attachToActivity(mActivity);
}
public void setSwipeEdge(int edgeFlag) {
mBaseSwipeLayout.setSwipeEdge(edgeFlag);
}
}
BaseSwipeLayout
//核心代码，绑定到相应activity
public void attachToActivity(Activity activity) {
this.mActivity = activity;
TypedArray a = activity.getTheme().obtainStyledAttributes(new int[]{
android.R.attr.windowBackground
});
int background = a.getResourceId(0, 0);
a.recycle();
ViewGroup decorView = (ViewGroup) activity.getWindow().getDecorView();
ViewGroup decorChild = (ViewGroup) decorView.getChildAt(0);
decorChild.setBackgroundResource(background);
decorView.removeView(decorChild);
addView(decorChild);
decorView.addView(this);
}
需要添加滑动退出的activity，添加想要代码
private SwipeHelper mSwipeHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view_drag_helper_act_layout);
mSwipeHelper = new SwipeHelper(this);
mSwipeHelper.onActivityCreate();
mSwipeHelper.setSwipeEdge(ViewDragHelper.EDGE_RIGHT);
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
mSwipeHelper.onPostCreate();
}
2016-02-23 15_17_01.gif
到此我们的代码基本完成，源码我放到了BaseSwipe，欢迎指教！
