滑动关闭activity，滑动activity

滑动关闭activity，滑动activity

对于微信滑动关闭activity的功能，我一直觉得挺酷，想在自己的项目上也加上这个功能。网上找了一下发现一个不错的思路。

使用ViewDragHelper。

首先要让activity在滑动的时候下面的activity能够看得到，那么就得设置activity的主题，让activity的窗口变透明。

<style name="MyActivityBackground" parent="MyAppTheme">
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:windowIsTranslucent">true</item>
        <item name="android:windowAnimationStyle">@android:style/Animation.Activity</item>
</style>

该主题继承MyAppTheme（这也是个自定义的主题，整个application就是用这个主题，为了不避免冲突，继承它）。
尤其要注意的是windowAnimationStyle，这个是设置activity的进入与退出的动画效果，设置为默认的效果。

然后在需要实现滑动退出的activity的注册文件上用上这个主题就行了。

 以下是全部代码

public class MyDragViewGroup extends FrameLayout{

    private ViewDragHelper mViewDragHelper;

    //该自定义组件的宽
    private int mWidth;

    //该自定义组件的高
    private int mHeight;

    //需要滑动的组件目前已经滑动的距离
    private int currentLeft;

    //该滑动距离用于判断是否可以将activity关闭
    private int mSlidX;

    private static final int x=40;
    private Context mContext;

    //需要滑动的view
    private View view;

    private Paint mPaint;

    public MyDragViewGroup(Context context) {
        super(context);
        initView(context);
    }

    public void bind()
    {
        //获取activity的视图
        ViewGroup viewGroup= (ViewGroup) ((Activity)mContext).getWindow().getDecorView();
        view=viewGroup.getChildAt(0);

        viewGroup.removeView(view); //将该视图移除
        addView(view);  //将该视图添加进去这个自定义的组件
        viewGroup.addView(this); //将该自定义的组件整个添加进decorView
    }


    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mWidth=getMeasuredWidth();
        mHeight=getMeasuredHeight();
        mSlidX= (int) (mWidth*0.3);
    }

    private void initView(Context context)
    {
        mContext=context;

        mViewDragHelper=ViewDragHelper.create(this,callback);
        //边缘检测
        mViewDragHelper.setEdgeTrackingEnabled(ViewDragHelper.EDGE_LEFT);

        mPaint=new Paint();
        mPaint.setStrokeWidth(2);
        mPaint.setAntiAlias(true);
        mPaint.setColor(Color.GRAY);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        return mViewDragHelper.shouldInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mViewDragHelper.processTouchEvent(event);
        return true;
    }


    private ViewDragHelper.Callback callback=new ViewDragHelper.Callback() {
        @Override
        public boolean tryCaptureView(View child, int pointerId) {
            return false;
        }

        @Override
        public int clampViewPositionVertical(View child, int top, int dy) {
            return 0;
        }

        @Override
        public int clampViewPositionHorizontal(View child, int left, int dx) {
            return left;
        }

        @Override
        public void onViewReleased(View releasedChild, float xvel, float yvel) {
            super.onViewReleased(releasedChild, xvel, yvel);

            //如果滑动的距离小于mSlidX，那么就滑回原处
            if (view.getLeft()<mSlidX)
            {
                mViewDragHelper.smoothSlideViewTo(view,0,0);
                ViewCompat.postInvalidateOnAnimation(MyDragViewGroup.this);
            }
            //否则滑出屏幕
            else
            {
                mViewDragHelper.smoothSlideViewTo(view,mWidth,0);
                ViewCompat.postInvalidateOnAnimation(MyDragViewGroup.this);
            }
            invalidate();
        }

        @Override
        public void onEdgeDragStarted(int edgeFlags, int pointerId) {
            mViewDragHelper.captureChildView(view,pointerId);
        }

        @Override
        public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
            currentLeft=left;
            invalidate();
            if (left>=mWidth)
            {
                ((Activity)mContext).finish();
            }
        }
    };

    @Override
    public void computeScroll() {
        if (mViewDragHelper.continueSettling(true))
        {
            ViewCompat.postInvalidateOnAnimation(this);
            invalidate();
        }
    }

    @Override
    protected void dispatchDraw(Canvas canvas) {
        drawShadow(canvas);
        super.dispatchDraw(canvas);
    }

    protected void drawShadow(Canvas canvas) {
        canvas.save();

        Shader mShader=new LinearGradient(currentLeft - x, 0, currentLeft, 0, new int[]{Color.parseColor("#1edddddd"),
                Color.parseColor("#6e666666"), Color.parseColor("#9e666666")}, null, Shader.TileMode.REPEAT);
        mPaint.setShader(mShader);
        //绘制时，注意向左边偏移
        RectF rectF = new RectF(currentLeft - x, 0, currentLeft, mHeight);
        canvas.drawRect(rectF, mPaint);
        canvas.restore();
    }
}

如果知道ViewDragHelper的使用，那么上面的代码很容易看得明白。drawShadow()是为了绘制阴影，注意在滑动的过程中要不断的刷新重绘，让阴影跟随着activity的移动而移动。

值得注意的是ViewGroup容器组件的绘制，当它没有背景时直接调用的是dispatchDraw()