Android ScrollView回弹效果（一）修改版

最新推荐文章于 2024-05-09 15:16:32 发布

原创最新推荐文章于 2024-05-09 15:16:32 发布 · 6.2k 阅读

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文章探讨了原ScrollView回弹效果的不足，特别是在内容过多时出现的卡顿问题，并介绍了一种能提升效率的替代实现方法。

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之前忘记在哪里看的demo，然后我修改了一下，希望之前那位仁兄不要见怪啊。

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.TranslateAnimation;
import android.widget.ScrollView;

public class CustomerScrollView3 extends ScrollView {

	Context mContext;
	private View mView;
	private Rect mRect = new Rect();
	private float touchY;

	private static final int MAX_SCROLL_HEIGHT = 200;// 最大滑动距离
	private static final float SCROLL_RATIO = 0.5f;// 阻尼系数

	public CustomerScrollView3(Context context) {
		super(context);
		this.mContext = context;
	}

	public CustomerScrollView3(Context context, AttributeSet attrs) {
		super(context, attrs);
		this.mContext = context;
	}

	public CustomerScrollView3(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		this.mContext = context;
	}

	@Override
	protected void onFinishInflate() {
		if (getChildCount() > 0) {
			this.mView = getChildAt(0);
		}
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent arg0) {
		if (arg0.getAction() == MotionEvent.ACTION_DOWN) {
			touchY = arg0.getY();
		}
		return super.onInterceptTouchEvent(arg0);
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		if (mView == null) {
			return super.onTouchEvent(ev);
		} else {
			commonOnTouchEvent(ev);
		}
		return super.onTouchEvent(ev);
	}

	private void commonOnTouchEvent(MotionEvent ev) {
		int action = ev.getAction();
		switch (action) {
		case MotionEvent.ACTION_DOWN:
			touchY = ev.getY();
			break;
		case MotionEvent.ACTION_UP:
			if (isNeedAnimation()) {
				animation();
			}
			break;
		case MotionEvent.ACTION_MOVE:
			final float preY = touchY;
			float nowY = ev.getY();
			int deltaY = (int) (preY - nowY);
			touchY = nowY;
			if (isNeedMove()) {
				if (mRect.isEmpty()) {
					mRect.set(mView.getLeft(), mView.getTop(), mView.getRight(), mView.getBottom());
				}
				int offset = mView.getTop() - deltaY;
				if (offset < MAX_SCROLL_HEIGHT && offset > -MAX_SCROLL_HEIGHT) {
					mView.layout(mView.getLeft(), mView.getTop() - (int) (deltaY * SCROLL_RATIO), mView.getRight(), mView.getBottom()
							- (int) (deltaY * SCROLL_RATIO));
				}
			}
			break;
		default:
			break;
		}
	}

	private boolean isNeedMove() {
		int viewHight = mView.getMeasuredHeight();
		int srollHight = getHeight();
		int offset = viewHight - srollHight;
		int scrollY = getScrollY();

		if (scrollY == 0 || scrollY == offset) {
			return true;
		}
		return false;
	}

	private boolean isNeedAnimation() {
		return !mRect.isEmpty();
	}

	private void animation() {
		TranslateAnimation ta = new TranslateAnimation(0, 0, mView.getTop(), mRect.top);
		ta.setDuration(200);
		mView.startAnimation(ta);
		mView.layout(mRect.left, mRect.top, mRect.right, mRect.bottom);
		mRect.setEmpty();

	}

}

这样做有一个不好的缺点就是，当ScrollView里面的内容很多的时候，感觉有点卡的，效率不好。

后面我用另外一种方法，效果稍微好点。