仿鲜果网切换activity

1. 鲜果网切换activity的效果就是滑动当前activity时，当前activity随手指滑动，而且上一个activity要在下面漏出来，当手指离开屏幕时，activity根据移动的位置关闭当前activity或者移动回原位。


2. 首先上一个activity作为当前activity的背景的实现是获取上一个activity的decorview，也就是根view，然后截图，把这个截图给当前activity作为背景。

// 获取根布局
final ViewGroup rootView = (ViewGroup) MainActivity.this
           .getWindow().getDecorView();
rootView.setDrawingCacheEnabled(true);
Constants.bitmap = rootView.getDrawingCache();
Intent intent = new Intent();
intent.setClass(MainActivity.this, SecondActivity. class);
startActivity(intent);

3. 当前activity中，布局如下：

<qingfengmy.testdemo.RootView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/rootview"
    android:layout_width= "match_parent"
    android:layout_height= "match_parent" >


    <RelativeLayout
        android:id= "@+id/layout"
        android:layout_width= "match_parent"
        android:layout_height= "match_parent"
        android:background= "#ff00ffff" >


        <TextView
            android:id= "@+id/tv"
            android:layout_width= "wrap_content"
            android:layout_height= "wrap_content"
            android:background= "#ff0000"
            android:text= "@string/hello_world"
            android:textColor= "#ffffff" />
    </RelativeLayout >


</qingfengmy.testdemo.RootView>

4. rootview设置背景为上一个activity的截图。


5. rootview加touch监听

rootView.setOnTouchListener( new OnTouchListener() {


     private int xx;


     @Override
     public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction()) {
            case MotionEvent. ACTION_DOWN:
                 startx = ( int) event.getX();
                 starty = ( int) event.getY();
                 beginx = startx;
                 break;
            case MotionEvent. ACTION_MOVE:
                 int movex = ( int) event.getX();
                 int movey = ( int) event.getY();
                 xx = movex - startx;
                 int xxx = movex - beginx;
                 if (xxx > 0 && xxx < windowWidth) {
                     Log. i("zt" , xxx + "=xxx;beginx=" + beginx);
                     Log. i("zt" , xx + "=xx;startx=" + startx );
                      rootView.scrollBy(- xx, 0);
                }
                 startx = movex;
                 starty = movey;
                 break;
            case MotionEvent. ACTION_UP:
                 // 算activity左边距在屏幕的位置
                 xx = ( int) (event.getX() - beginx);
                Log. i("zt" , xx + ".windowWidth=" + windowWidth / 2);


                 if ( xx > windowWidth / 2) {
                     finish();
                } else {
                      int xxxx = rootView.getScrollX();
                     Log. i("zt" , xxxx + "=xxxx," );
                      rootView.beginScroll(xxxx);
                }
                 break;
            default:
                 break;
           }
            return true;
     }
});

6. rootview在up的时候，滚动回原位或者finish当前页面。其中滚动回原位的代码：

@Override
public void computeScroll() {
     super.computeScroll();
     if (mScroller.computeScrollOffset()) {
           scrollTo( mScroller.getCurrX(), 0);
           postInvalidate();
     }
}


public void beginScroll(int startX) {
     if (!s1) {
            mScroller.startScroll(startX, 0, -startX, 0, Math.abs(startX)/6*15);
            s1 = true;
     } else {
            mScroller.startScroll(startX, 0, -startX, 0, Math.abs(startX)/6*15);
            s1 = false;
     }
     invalidate();
}