GestureDetector封装手势检測上下滑动

项目中须要检測ListView的上滑下滑隐藏顶部View控件，之前在网上也有非常多实现案例。在git上发现个封装非常不错的样例，记录下来。

GestureDetector是一个手势检測类，内部有个SimpleOnGestureListener手势监听类。

定义一个抽象类SimpleDetector。继承GestureDetector.SimpleOnGestureListener抽象类，实现View.OnTouchListener接口。这样做有什么优点呢？首先ListView仅仅要setOnTouchListener。把定义的这个抽象类SimpleDetector设置进就好。然后这个类SimpleDetector仅仅须要负责检測上滑还是下滑事件。逻辑得到了分离。

为了要实现ListView顶部View控件的动画效果，须要定义另外一个类继承上面抽象的SimpleDetector类，在这个类里单独处理上滑下滑时候须要运行的动画或者其他逻辑事件。上面的SimpleDetector抽象类提供两个抽象方法供子类去实现。这样整个封装就显得很完美了。

public abstract class SimpleDetector extends GestureDetector.SimpleOnGestureListener implements View.OnTouchListener{

	private final GestureDetector mDetector;
	private final int mSlop;//slop晃荡的意思
	private boolean mIgnore;//是否忽略监听上下滚动
	private float mDownY;
	
	public abstract void onScrollDown();
	public abstract void onScrollUp();
	
	public SimpleDetector(Context context){
		mDetector = new GestureDetector(context,this);
		mSlop = getSlop(context);
	}
	
	public boolean isIgnore() {
		return mIgnore;
	}
	public void setIgnore(boolean mIgnore) {
		this.mIgnore = mIgnore;
	}
	protected int getSlop(Context context){
		if(Build.VERSION.SDK_INT < Build.VERSION_CODES.FROYO){
			return ViewConfiguration.getTouchSlop() * 2;
		}else{
			return ViewConfiguration.get(context).getScaledPagingTouchSlop();
		}
	}
	
	@Override
	public boolean onDown(MotionEvent e) {
		// TODO Auto-generated method stub
		mDownY = e.getY();
		return false;
	}
	
	@Override
	public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
			float distanceY) {
		// TODO Auto-generated method stub
		if(mIgnore)
			return false;
		if(distanceY==0){
			mDownY = e2.getY();
		}
		
		float distance = mDownY - e2.getY();
		
		if(distance < -mSlop){
			onScrollDown();
		}else if(distance > mSlop){
			onScrollUp();
		}
		return false;
	}
	
	@Override
	public boolean onTouch(View v, MotionEvent event) {
		// TODO Auto-generated method stub
		mDetector.onTouchEvent(event);
		return false;
	}

}

public class ShowHideOnScroll extends SimpleDetector implements AnimatorListener{

	private final View mView;
	private int mShowAnimation;
	private int mHideAnimation;
	private int mTranslationY;
	private int curShowHide = 0;
	
	public ShowHideOnScroll(View view,int translationY){
		super(view.getContext());
		mView = view;
		mTranslationY = translationY;
	}
	
	public ShowHideOnScroll(View view,int show,int hide,int translationY) {
		super(view.getContext());
		mView = view;
		mShowAnimation = show;
		mHideAnimation = hide;
		mTranslationY = translationY;
	}

	@Override
	public void onScrollDown() {
		mView.setVisibility(View.VISIBLE);
		animateShow();
		curShowHide = 0;
	}

	@Override
	public void onScrollUp() {
		mView.setVisibility(View.VISIBLE);
		animateHide();
		curShowHide = 1;
	}
	private void animateShow(){
		mView.setTranslationY(mTranslationY);
		mView.animate().translationY(0).setInterpolator(new AccelerateDecelerateInterpolator())
		.setStartDelay(0).setDuration(400).setListener(ShowHideOnScroll.this).start();
		setIgnore(true);
	}
	private void animateHide(){
		mView.setTranslationY(0);
		mView.animate().translationY(mTranslationY).setInterpolator(new AccelerateDecelerateInterpolator())
		.setStartDelay(0).setDuration(400).setListener(ShowHideOnScroll.this).start();
		setIgnore(true);
	}

	@Override
	public void onAnimationStart(Animator animation) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void onAnimationEnd(Animator animation) {
		// TODO Auto-generated method stub
		if(curShowHide==0){
			mView.setVisibility(View.VISIBLE);
			mView.setTranslationY(0);
		}else if(curShowHide == 1){
			mView.setVisibility(View.INVISIBLE);
			mView.setTranslationY(mTranslationY);
		}
		setIgnore(false);
	}

	@Override
	public void onAnimationCancel(Animator animation) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void onAnimationRepeat(Animator animation) {
		// TODO Auto-generated method stub
		
	}
	


}

这个能够举一反三运用到其他地方去，以后写代码框架非常重要。事物逻辑要做到分离。这样代码写的非常完美无可挑剔。

在新公司上了一个多月班了。压力山大，全是高材生，研究生也来写代码，真心的~然后又被boss当着研究实习生面训了一次。真心不好受。还是提高自己的能力，有时间自己多学习。有能力了不用去苦心证明自己