采用Scroller实现任意布局的上下左右弹性效果

不知道Scroller是什么的同志先看下面：
Android Scroller类的详细分析

这里采用Scroller实现类似iphone的上下拖拉弹性效果，具体代码如下：

import android.content.Context;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.widget.LinearLayout;
import android.widget.Scroller;

public class BouncyLinearLayout extends LinearLayout {

	private static final String TAG = "BouncyLinearLayout";
	private Scroller mScroller;
	private GestureDetector mGestureDetector;
	
	public BouncyLinearLayout(Context context) {
		this(context, null);
	}
	
	public BouncyLinearLayout(Context context, AttributeSet attrs) {
		super(context, attrs);
		setClickable(true);
		setLongClickable(true);
		mScroller = new Scroller(context);
		mGestureDetector = new GestureDetector(context, new BouncyGestureListener());
	}

	/**
	 * 滚动到目标位置
	 * @param fx
	 * @param fy
	 */
	protected void smoothScrollTo(int fx, int fy) {
		int dx = fx - mScroller.getFinalX();
		int dy = fy - mScroller.getFinalY();
		smoothScrollBy(dx, dy);
	}

	/**
	 * 设置滚动的相对偏移
	 * @param dx
	 * @param dy
	 */
	protected void smoothScrollBy(int dx, int dy) {
		//设置mScroller的滚动偏移量
		mScroller.startScroll(mScroller.getFinalX(), mScroller.getFinalY(), dx, dy);
		invalidate();//这里必须调用invalidate()才能保证computeScroll()会被调用，否则不一定会刷新界面，看不到滚动效果
	}
	
	@Override
	public void computeScroll() {
		//判断mScroller滚动是否完成
		if (mScroller.computeScrollOffset()) {
			//这里调用View的scrollTo()完成实际的滚动
			scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
			//必须调用该方法，否则不一定能看到滚动效果
			postInvalidate();
		}
		super.computeScroll();
	}
	
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		switch (event.getAction()) {
		case MotionEvent.ACTION_UP :
			smoothScrollTo(0, 0);
			break;
		default:
			return mGestureDetector.onTouchEvent(event);
		}
		return super.onTouchEvent(event);
	}
	
	class BouncyGestureListener implements GestureDetector.OnGestureListener {

		@Override
		public boolean onDown(MotionEvent e) {
			// TODO Auto-generated method stub
			return true;
		}

		@Override
		public void onShowPress(MotionEvent e) {
			// TODO Auto-generated method stub
			
		}

		@Override
		public boolean onSingleTapUp(MotionEvent e) {
			// TODO Auto-generated method stub
			return false;
		}

		@Override
		public boolean onScroll(MotionEvent e1, MotionEvent e2,
				float distanceX, float distanceY) {
			int dis = (int)((distanceY-0.5)/2);
			smoothScrollBy(0, dis);
			return false;
		}

		@Override
		public void onLongPress(MotionEvent e) {
			// TODO Auto-generated method stub
			
		}

		@Override
		public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
				float velocityY) {
			// TODO Auto-generated method stub
			return false;
		}
		
	}
}

以上代码只需要稍加改动就可以上下左右4个方向上的弹性效果了
看下面代码，只在BouncyGestureListener的onScroll方法中加了X方向的位移。

import android.content.Context;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.widget.LinearLayout;
import android.widget.Scroller;

public class BouncyLinearLayout extends LinearLayout {

	private static final String TAG = "BouncyLinearLayout";
	private Scroller mScroller;
	private GestureDetector mGestureDetector;
	
	public BouncyLinearLayout(Context context) {
		this(context, null);
	}
	
	public BouncyLinearLayout(Context context, AttributeSet attrs) {
		super(context, attrs);
		setClickable(true);
		setLongClickable(true);
		mScroller = new Scroller(context);
		mGestureDetector = new GestureDetector(context, new BouncyGestureListener());
	}

	/**
	 * 滚动到目标位置
	 * @param fx
	 * @param fy
	 */
	protected void smoothScrollTo(int fx, int fy) {
		int dx = fx - mScroller.getFinalX();
		int dy = fy - mScroller.getFinalY();
		smoothScrollBy(dx, dy);
	}

	/**
	 * 设置滚动的相对偏移
	 * @param dx
	 * @param dy
	 */
	protected void smoothScrollBy(int dx, int dy) {
		//设置mScroller的滚动偏移量
		mScroller.startScroll(mScroller.getFinalX(), mScroller.getFinalY(), dx, dy);
		invalidate();//这里必须调用invalidate()才能保证computeScroll()会被调用，否则不一定会刷新界面，看不到滚动效果
	}
	
	@Override
	public void computeScroll() {
		//判断mScroller滚动是否完成
		if (mScroller.computeScrollOffset()) {
			//这里调用View的scrollTo()完成实际的滚动
			scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
			//必须调用该方法，否则不一定能看到滚动效果
			postInvalidate();
		}
		super.computeScroll();
	}
	
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		switch (event.getAction()) {
		case MotionEvent.ACTION_UP :
			smoothScrollTo(0, 0);
			break;
		default:
			return mGestureDetector.onTouchEvent(event);
		}
		return super.onTouchEvent(event);
	}
	
	class BouncyGestureListener implements GestureDetector.OnGestureListener {

		@Override
		public boolean onDown(MotionEvent e) {
			// TODO Auto-generated method stub
			return true;
		}

		@Override
		public void onShowPress(MotionEvent e) {
			// TODO Auto-generated method stub
			
		}

		@Override
		public boolean onSingleTapUp(MotionEvent e) {
			// TODO Auto-generated method stub
			return false;
		}

		@Override
		public boolean onScroll(MotionEvent e1, MotionEvent e2,
				float distanceX, float distanceY) {
			int disX = (int)((distanceX-0.5)/2);
			int disY = (int)((distanceY-0.5)/2);
			smoothScrollBy(disX, disY);
			return false;
		}

		@Override
		public void onLongPress(MotionEvent e) {
			// TODO Auto-generated method stub
			
		}

		@Override
		public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
				float velocityY) {
			// TODO Auto-generated method stub
			return false;
		}
		
	}
}

一个iOS风格的边缘弹性效果，支持几乎所有滚动视图
http://www.jcodecraeer.com/a/opensource/2015/1205/3753.html

评论

1 楼 andywahaha 2014-04-03  

如果内嵌scrollView 或者listview，好像就失效了