Android实现下拉放大图片松手自动反弹效果

本文实例为大家分享了Android实现下拉放大图片松手自动反弹的具体代码，供大家参考，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

下面是布局activity_main

<bwie.com.pulllistview.HeadZoomScrollView
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/scrollView"
  android:layout_width="match_parent"
  android:layout_height="match_parent"> 

  <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"> 

    <ImageView
      android:id="@+id/iv_show"
      android:layout_width="match_parent"
      android:layout_height="200dp"
      android:layout_weight="1"
      android:src="@drawable/a1"/>
    <TextView
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="数据1"/>
    <TextView
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="数据2"/>
    <TextView
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="数据3"/>
    <TextView
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="数据4"/> 

  </LinearLayout> 

</bwie.com.pulllistview.HeadZoomScrollView> 

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我们。

您可能感兴趣的文章:

• Android ListView实现下拉顶部图片变大效果
• Android仿QQ好友详情页下拉顶部图片缩放效果
• Android DragImageView实现下拉拖动图片放大效果
• android ScrollView实现下拉放大头部图片
• Android自定义scrollView实现顶部图片下拉放大
• Android开发重写Animation实现下拉图片后弹射回去效果示例