本文实例为大家分享了scrollView实现顶部图片下拉放大的具体代码，供大家参考，具体内容如下

之前的scrollView顶部图片下拉放大在之后的项目用到了几次，但没次都写在Activity中很麻烦，也不方便复用。这几天有空，所以重新使用自定义scrollView的方法实现这个效果。原理和之前的基本是一致的，所以也不多说了，直接上代码。

package com.example.myapplication.dropzoom; import android.animation.ObjectAnimator; 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 Liujinhua on 2016/3/25. * 下拉放大scrollView */ public class DropZoomScrollView extends ScrollView implements View.OnTouchListener { // 记录首次按下位置 private float mFirstPosition = 0; // 是否正在放大 private Boolean mScaling = false; private View dropZoomView; private int dropZoomViewWidth; private int dropZoomViewHeight; public DropZoomScrollView(Context context) { super(context); } public DropZoomScrollView(Context context, AttributeSet attrs) { super(context, attrs); } public DropZoomScrollView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); } @Override protected void onFinishInflate() { super.onFinishInflate(); init(); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); } private void init() { setOverScrollMode(OVER_SCROLL_NEVER); if (getChildAt(0) != null) { ViewGroup vg = (ViewGroup) getChildAt(0); if (vg.getChildAt(0) != null) { dropZoomView = vg.getChildAt(0); setOnTouchListener(this); } } } @Override public boolean onTouch(View v, MotionEvent event) { if (dropZoomViewWidth <= 0 || dropZoomViewHeight <= 0) { dropZoomViewWidth = dropZoomView.getMeasuredWidth(); dropZoomViewHeight = dropZoomView.getMeasuredHeight(); } switch (event.getAction()) { case MotionEvent.ACTION_UP: //手指离开后恢复图片 mScaling = false; replyImage(); break; case MotionEvent.ACTION_MOVE: if (!mScaling) { if (getScrollY() == 0) { mFirstPosition = event.getY();// 滚动到顶部时记录位置，否则正常返回 } else { break; } } int distance = (int) ((event.getY() - mFirstPosition) * 0.6); // 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 mScaling = true; setZoom(1 + distance); return true; // 返回true表示已经完成触摸事件，不再处理 } return false; } // 回弹动画 (使用了属性动画) public void replyImage() { final float distance = dropZoomView.getMeasuredWidth() - dropZoomViewWidth; // 设置动画 ValueAnimator anim = ObjectAnimator.ofFloat(0.0F, 1.0F).setDuration((long) (distance * 0.7)); anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { float cVal = (Float) animation.getAnimatedValue(); setZoom(distance - ((distance) * cVal)); } }); anim.start(); } //缩放 public void setZoom(float s) { if (dropZoomViewHeight <= 0 || dropZoomViewWidth <= 0) { return; } ViewGroup.LayoutParams lp = dropZoomView.getLayoutParams(); lp.width = (int) (dropZoomViewWidth + s); lp.height = (int) (dropZoomViewHeight * ((dropZoomViewWidth + s) / dropZoomViewWidth)); dropZoomView.setLayoutParams(lp); } }

使用的时候也十分的简单

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <com.example.myapplication.dropzoom.DropZoomScrollView android:layout_width="match_parent" android:layout_height="match_parent"> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical"> <ImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:src="@drawable/bg" /> <ImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:src="@drawable/home_bg" /> <ImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:src="@drawable/home_bg" /> <ImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:src="@drawable/home_bg" /> <ImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:src="@drawable/home_bg" /> </LinearLayout> </com.example.myapplication.dropzoom.DropZoomScrollView> </LinearLayout>

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。