侧滑效果[第十篇]：侧滑框架SmartSwipe之仿手机QQ侧滑

拿起手机，打开QQ，随便找个页面再随便侧滑一下，发现当前Activity执行关闭了，当放慢侧滑速率时不会触发Activity返回效果。

SmartSwipe框架的StayConsumer可以根据侧滑速率实现类似手机QQ的返回效果。

StayConsumer的代码如下：

/**
 * Swipe to do something, the contentView do not move,
 *  when swipe released, determine whether the velocity and direction is enough, do some business if success
 * @author billy.qi
 */
public class StayConsumer extends SwipeConsumer {
    private int mMinVelocity = 1000;

    public StayConsumer() {
        setOpenDistance(Integer.MAX_VALUE)
                .setMaxSettleDuration(0);
    }

    @Override
    protected void onDisplayDistanceChanged(int distanceXToDisplay, int distanceYToDisplay, int dx, int dy) {
        //do nothing
    }

    @Override
    public void onSwipeReleased(float xVelocity, float yVelocity) {
        if (Math.abs(xVelocity) > Math.abs(yVelocity)) {
            if (mDirection == DIRECTION_LEFT && xVelocity >= mMinVelocity || (mDirection == DIRECTION_RIGHT && xVelocity <= -mMinVelocity)) {
                mCurSwipeDistanceX = getSwipeOpenDistance();
                mProgress = 1;
            }
        } else {
            if (mDirection == DIRECTION_TOP && yVelocity >= mMinVelocity || (mDirection == DIRECTION_BOTTOM && yVelocity <= -mMinVelocity)) {
                mCurSwipeDistanceY = getSwipeOpenDistance();
                mProgress = 1;
            }
        }
        super.onSwipeReleased(xVelocity, yVelocity);
    }

    public int getMinVelocity() {
        return mMinVelocity;
    }

    public StayConsumer setMinVelocity(int minVelocity) {
        if (minVelocity > 0) {
            this.mMinVelocity = minVelocity;
        }
        return this;
    }
}

mMinVelocity为最小速度，当滑动速度超过这个最小值时，mProgress从0变成1，也就是说从默认的关闭状态立即切换到打开状态。

换一种说法是：主体contentView在侧滑过程中保持不动，侧滑结束时按照手势滑动的方向和速率来确定是否开启，若开启将回调[SwipeListener]的onSwipeOpen方法。

效果如下：

从效果图中看不到侧滑的效果，因为StayConsumer是没有侧滑效果的，它只有计算侧滑方向和速率的实现。

代码实现如下：

    SmartSwipe.wrap(this)
            .addConsumer(new StayConsumer())
            .enableAllDirections()
            .addListener(new SimpleSwipeListener(){

                @Override
                public void onSwipeOpened(SmartSwipeWrapper wrapper, SwipeConsumer consumer, int direction) {
                //关闭当前界面
                    ImageViewerActivity.this.finish();
                }
    });

[本章完...]