android scroller用法

Scroller不是视图控件，只是用于控制滚动

Scroller几个重要方法

void	startScroll(int startX, int startY, int dx, int dy) Start scrolling by providing a starting point and the distance to travel.
void	startScroll(int startX, int startY, int dx, int dy, int duration)

	abortAnimation() Stops the animation.
boolean	computeScrollOffset() Call this when you want to know the new location.
void	fling(int startX, int startY, int velocityX, int velocityY, int minX, int maxX, int minY, int maxY) Start scrolling based on a fling gesture.
final void	forceFinished(boolean finished) Force the finished field to a particular value.

startScroll用于开始滚动，默认时间为250ms，

computeScrollerOffset用于计算滚动的的位置

fling用于控制快速滑动松开后，根据velocityX，Y继续滚动一段距离

下面一个简单的自定义view实现水平滚动，为了简单，我们直接使用GestureDetector类去处理触摸事件，通过回调处理滚动事件

@TargetApi(9)
public class CustomeScrollView extends FrameLayout {
	private OverScroller scroller;
	private GestureDetector detector;

	public CustomeScrollView(Context context) {
		this(context,null);
		// TODO Auto-generated constructor stub
	}
	public CustomeScrollView(Context context,AttributeSet set){
		this(context, set,0);
		
	}
	public CustomeScrollView(Context context,AttributeSet set,int def){
		super(context,set,def);	
		scroller=new OverScroller(context,new AccelerateInterpolator());
		detector=new GestureDetector(context, new SimpleGestureListener());
	}
	//调用startScroll可以进行滚动
	public void startScroll(){
		scroller.startScroll(0, 0,-400 , 0, 1000);
		invalidate();
		
	}
	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		// TODO Auto-generated method stub
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		int count=getChildCount();
		int width=0;
		for (int i = 0; i < count; i++) {
			View  child=getChildAt(i);
			if(i==0){
				
				child.measure(getChildMeasureSpec(MeasureSpec.UNSPECIFIED, 0, 200), heightMeasureSpec);	
			}else{
				child.measure(widthMeasureSpec, heightMeasureSpec);	
			}
		
			width+=child.getWidth();
			
		}
		setMeasuredDimension(width, heightMeasureSpec);
	}
	
	@Override
	protected void onLayout(boolean changed, int left, int top, int right,
			int bottom) {
		// TODO Auto-generated method stub
		super.onLayout(changed, left, top, right, bottom);
		int count=getChildCount();
		for (int i = 0; i < count; i++) {
			View  child=getChildAt(i);
			child.layout(left, top, left+child.getWidth(), top+child.getHeight());
			left+=child.getWidth();
		  }
	  scrollTo(200, 0);
	}
	
	@Override
	public void computeScroll() {
		// TODO Auto-generated method stub
		//super.computeScroll();
              //自定义view必须实现computeScroll函数，调用Scroller.computeScorllOffset去计算当前滚动的位置，滚动到终点，computeScrollOffset返回false
               if(scroller.computeScrollOffset()){
			scrollTo(-scroller.getCurrX(), 0);
			postInvalidate();
			
		}
	
	}
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		// TODO Auto-generated method stub
		/// super.onTouchEvent(event);
		// super.onTouchEvent(event);
		 switch (event.getAction()) {
		case MotionEvent.ACTION_DOWN:
			scroller.forceFinished(true);
			break;
		case MotionEvent.ACTION_CANCEL:
		case MotionEvent.ACTION_UP:
			break;
		 default:
			break;
		}
		detector.onTouchEvent(event);
		 return true;
	}
	class SimpleGestureListener extends GestureDetector.SimpleOnGestureListener{

		@Override
		public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
				float velocityY) {
			// TODO Auto-generated method stub
	 scroller.fling(scroller.getCurrX(), scroller.getCurrY(), (int)velocityX, (int)velocityY, -200, 0, 0,0);
			invalidate();
			return true;
		}

		@Override
		public boolean onScroll(MotionEvent e1, MotionEvent e2,
				float distanceX, float distanceY) {
			// TODO Auto-generated method stub
		     scrollBy((int)distanceX,0);
			invalidate();
			return true;
		}
		
		
	}

}

Activity代码，两个imageView
public class MainActivity extends Activity {
	@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        final CustomeScrollView view=new CustomeScrollView(this);
        view.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.MATCH_PARENT));
      //  view.setBackgroundColor(Color.RED);
        ImageView image =new ImageView(this);
        image.setLayoutParams(new LayoutParams(300, LayoutParams.MATCH_PARENT));
        image.setBackgroundColor(Color.RED);
        view.addView(image);
        ImageView image2 =new ImageView(this);
        image2.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
        image2.setBackgroundColor(Color.BLUE);
        view.addView(image2);
        setContentView(view);
 
    }

    

    }
  

OverScroller和Scroller用法基本相同，不同点是OverScroller允许滚动超出边界，可以实现回弹效果