这篇文章主要介绍了Android如何实现下拉放大图片松手自动反弹效果，具有一定借鉴价值，感兴趣的朋友可以参考下，希望大家阅读完这篇文章之后大有收获，下面让小编带着大家一起了解一下。
具体内容如下
直接看效果：
下面就是代码
HeadZoomScrollView类
import android.animation.ValueAnimator; import android.content.Context; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; import android.view.ViewGroup; import android.widget.ScrollView; /** * Created by BAIPEI on 2017/11/21. */ public class HeadZoomScrollView extends ScrollView { private View mZoomView; private int mZoomViewWidth; private int mZoomViewHeight; private float firstPosition;//记录第一次按下的位置 private boolean isScrolling;//是否正在缩放 private float mScrollRate = 0.3f;//缩放系数，缩放系数越大，变化的越大 private float mReplyRate = 0.5f;//回调系数，越大，回调越慢 public HeadZoomScrollView(Context context) { super(context); } public HeadZoomScrollView(Context context, AttributeSet attrs) { super(context, attrs); } public HeadZoomScrollView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); } public void setmZoomView(View mZoomView) { this.mZoomView = mZoomView; } public void setmScrollRate(float mScrollRate) { this.mScrollRate = mScrollRate; } public void setmReplyRate(float mReplyRate) { this.mReplyRate = mReplyRate; } @Override protected void onFinishInflate() { super.onFinishInflate(); init(); } private void init() { setOverScrollMode(OVER_SCROLL_NEVER); if (getChildAt(0) != null) { ViewGroup vg = (ViewGroup) getChildAt(0); if (vg.getChildAt(0) != null) { mZoomView = vg.getChildAt(0); } } } @Override public boolean onTouchEvent(MotionEvent ev) { if (mZoomViewWidth <= 0 || mZoomViewHeight <= 0) { mZoomViewWidth = mZoomView.getMeasuredWidth(); mZoomViewHeight = mZoomView.getMeasuredHeight(); } switch (ev.getAction()) { case MotionEvent.ACTION_UP: //手指离开后恢复图片 isScrolling = false; replyImage(); break; case MotionEvent.ACTION_MOVE: if (!isScrolling) { if (getScrollY() == 0) { firstPosition = ev.getY();// 滚动到顶部时记录位置，否则正常返回 } else { break; } } int distance = (int) ((ev.getY() - firstPosition) * mScrollRate); // 滚动距离乘以一个系数 if (distance < 0) { // 当前位置比记录位置要小，正常返回 break; } // 处理放大 isScrolling = true; setZoom(distance); return true; // 返回true表示已经完成触摸事件，不再处理 } return true; } //回弹动画 private void replyImage() { float distance = mZoomView.getMeasuredWidth() - mZoomViewWidth; ValueAnimator valueAnimator = ValueAnimator.ofFloat(distance, 0f).setDuration((long) (distance * mReplyRate)); valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { setZoom((Float) animation.getAnimatedValue()); } }); valueAnimator.start(); } public void setZoom(float zoom) { if (mZoomViewWidth <= 0 || mZoomViewHeight <= 0) { return; } ViewGroup.LayoutParams lp = mZoomView.getLayoutParams(); lp.width = (int) (mZoomViewWidth + zoom); lp.height = (int) (mZoomViewHeight * ((mZoomViewWidth + zoom) / mZoomViewWidth)); ((MarginLayoutParams) lp).setMargins(-(lp.width - mZoomViewWidth) / 2, 0, 0, 0); mZoomView.setLayoutParams(lp); } }MainActivity里面没有写代码就不粘了
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