SwipeBackLayout.java

package com.wukongtv.wkremote.client.widget;


import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.Scroller;

/**
 * Created by sadieyu
 * Date: 15-1-20.
 */
public class SwipeBackLayout extends FrameLayout {
	private View mContentView;
	private int mTouchSlop;
	private int mDownX;
	private int mDownY;
	private int mTempX;
    /**
     *see {{@link Scroller} }
     */
	private Scroller mScroller;
	private int mViewWidth;
	private boolean mISilding;
	private boolean mIsFinish;
	private Activity mActivity;

	public SwipeBackLayout(Context context, AttributeSet attrs) {
		this(context, attrs, 0);
	}

	public SwipeBackLayout(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
		mScroller = new Scroller(context);
	}
	
	public void attachToActivity(Activity activity) {
		mActivity = activity;
        //get the background color (or Drawable) from the current theme
		TypedArray typedArray = activity.getTheme().obtainStyledAttributes(
				new int[] { android.R.attr.windowBackground });
		int background = typedArray.getResourceId(0, 0);
        typedArray.recycle();

        /**
         * {@link android.view.Window#getDecorView()}
         *
         * Retrieve the top-level window decor view (containing the standard
         * window frame/decorations and the client's content inside of that), which
         * can be added as a window to the window manager.
         */
		ViewGroup decor = (ViewGroup) activity.getWindow().getDecorView();
		ViewGroup decorChild = (ViewGroup) decor.getChildAt(0);
		decorChild.setBackgroundResource(background);
		decor.removeView(decorChild);
		addView(decorChild);
		setContentView(decorChild);
		decor.addView(this);
	}

	private void setContentView(View decorChild) {
		mContentView = (View) decorChild.getParent();
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		switch (ev.getAction()) {
		case MotionEvent.ACTION_DOWN:
			mDownX = mTempX = (int) ev.getRawX();
			mDownY = (int) ev.getRawY();
			break;
		case MotionEvent.ACTION_MOVE:
			int moveX = (int) ev.getRawX();
			if (moveX - mDownX > mTouchSlop
					&& Math.abs((int) ev.getRawY() - mDownY) < mTouchSlop) {
				return true;
			}
			break;
		}

		return super.onInterceptTouchEvent(ev);
	}

	@Override
	public boolean onTouchEvent(MotionEvent event) {
		switch (event.getAction()) {
		case MotionEvent.ACTION_MOVE:
			int moveX = (int) event.getRawX();
			int deltaX = mTempX - moveX;
			mTempX = moveX;
			if (moveX - mDownX > mTouchSlop
					&& Math.abs((int) event.getRawY() - mDownY) < mTouchSlop) {
				mISilding = true;
			}

			if (moveX - mDownX >= 0 && mISilding) {
				mContentView.scrollBy(deltaX, 0);
			}
			break;
		case MotionEvent.ACTION_UP:
			mISilding = false;
			if (mContentView.getScrollX() <= -mViewWidth / 2) {
				mIsFinish = true;
				scrollRight();
			} else {
				scrollOrigin();
				mIsFinish = false;
			}
			break;
		}

		return true;
	}
	

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		super.onLayout(changed, l, t, r, b);
		if (changed) {
			mViewWidth = this.getWidth();
		}
	}

	private void scrollRight() {
		final int delta = (mViewWidth + mContentView.getScrollX());
		mScroller.startScroll(mContentView.getScrollX(), 0, -delta, 0,
				Math.abs(delta));
		postInvalidate();
	}

	private void scrollOrigin() {
		int delta = mContentView.getScrollX();
		mScroller.startScroll(mContentView.getScrollX(), 0, -delta, 0,
				Math.abs(delta));
		postInvalidate();
	}

    /**
     * Called by a parent to request that a child update its values for mScrollX and mScrollY if necessary.
     * This will typically be done if the child is animating a scroll using a Scroller object.
     * so {@link View#computeScroll} can be invoked when
     * {@link android.view.View.OnTouchListener},
     * {@link android.view.View#invalidate()},
     * {@link android.view.View#postInvalidate()}
     */
	@Override
	public void computeScroll() {
		if (mScroller.computeScrollOffset()) {
			mContentView.scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
			postInvalidate();

			if (mScroller.isFinished() && mIsFinish) {
				mActivity.finish();
			}
		}
	}

}