AndroidDragImageView实现下拉拖动图片放大效果

DragImageView下拉拖动图片放大，先上图：

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Android DragImageView实现下拉拖动图片放大效果

主要的类：继承了RelativeLayout，再在RelativeLayout里面添加ImageView，通过Touch事件来改变ImageView的缩放，缩放时计算scale，使其在手指移动到屏幕底部时，图片底部也刚好到达屏幕底部，手指松开时，图片逐步回弹。

package com.example.dragimagescale; 
 
import android.annotation.SuppressLint; 
import android.app.Activity; 
import android.content.Context; 
import android.content.res.TypedArray; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.graphics.Matrix; 
import android.graphics.PointF; 
import android.os.Handler; 
import android.os.Message; 
import android.util.AttributeSet; 
import android.util.DisplayMetrics; 
import android.util.Log; 
import android.view.MotionEvent; 
import android.view.WindowManager; 
import android.widget.ImageView; 
import android.widget.ImageView.ScaleType; 
import android.widget.RelativeLayout; 
 
public class DragScaleImageView extends RelativeLayout { 
 private String TAG = "DragScaleImageView"; 
 private static final int BACK_SCALE = 1010; 
 
 private Context mContext; 
 private AttributeSet attrs; 
 private int displayWidth = 0; 
 private int displayHeight = 0; 
 private int mImageId; 
 private Bitmap bmp; 
 private ImageView imageView; 
 
 /** 是否处在回弹状态 */ 
 private boolean isBacking = false; 
 
 /** 用于记录拖拉图片移动的坐标位置 */ 
 private Matrix matrix = new Matrix(); 
 /** 用于记录图片要进行拖拉时候的坐标位置 */ 
 private Matrix currentMatrix = new Matrix(); 
 private Matrix defaultMatrix = new Matrix(); 
 /** 图片的宽高 */ 
 private float imgHeight, imgWidth; 
 /** 初始状态 */ 
 private int mode = 0; 
 /** 拖拉照片模式 */ 
 private final int MODE_DRAG = 1; 
 
 private float scaleY = 0; 
 
 /** 用于记录开始时候的坐标位置 */ 
 private PointF startPoint = new PointF(); 
 
 /** 用于记录开始时候的在整个屏幕中的Y坐标位置 */ 
 private float startRawY = 0; 
 float scale = 1; 
    
 private TouchEventListener touchEventListener = null; 
 private BackScaleListener backScaleListener = null; 
 
 public DragScaleImageView(Context context, AttributeSet attrs) { 
  super(context, attrs); 
  // TODO Auto-generated constructor stub 
  this.mContext = context; 
  this.attrs = attrs; 
  initView(); 
 } 
 
 public DragScaleImageView(Context context) { 
  super(context); 
  // TODO Auto-generated constructor stub 
  this.mContext = context; 
  initView(); 
 } 
 
 public DragScaleImageView(Activity activity, Bitmap resBitmap, int width, 
   int height) { 
  super(activity); 
 } 
 
 /** 
  * 初始化图片 
  */ 
 private void initView() { 
  /* 取得屏幕分辨率大小 */ 
  DisplayMetrics dm = new DisplayMetrics(); 
  WindowManager mWm = (WindowManager) mContext 
    .getSystemService(Context.WINDOW_SERVICE); 
  mWm.getDefaultDisplay().getMetrics(dm); 
  displayWidth = dm.widthPixels; 
  displayHeight = dm.heightPixels; 
 
  TypedArray a = mContext.obtainStyledAttributes(attrs, 
    R.styleable.DragScaleImageView); 
  mImageId = a.getResourceId(R.styleable.DragScaleImageView_scale_image, 
    0); 
  a.recycle(); 
  if (null == bmp && mImageId != 0) { 
   bmp = BitmapFactory.decodeResource(getResources(), mImageId); 
   float scale = (float) displayWidth / (float) bmp.getWidth();// 1080/1800 
   matrix.postScale(scale, scale, 0, 0); 
   imgHeight = scale * bmp.getHeight(); 
   imgWidth = scale * bmp.getWidth(); 
  } else { 
   imgHeight = displayWidth; 
   imgWidth = displayWidth; 
  } 
  initImageView(); 
 } 
 
 private void initImageView() { 
  imageView = new ImageView(mContext); 
  imageView.setImageMatrix(matrix); 
  defaultMatrix.set(matrix); 
  Log.w(TAG, "imgWidth :" + imgWidth); 
  Log.w(TAG, "imgHeight :" + imgHeight); 
 
  RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams( 
    (int) imgWidth, (int) imgHeight); 
  imageView.setLayoutParams(layoutParams); 
  imageView.setImageBitmap(bmp); 
  imageView.setScaleType(ScaleType.CENTER_CROP); 
  this.addView(imageView); 
 } 
 
 /** 
  * 设置ImageView的宽高 
  * 
  * @param width 
  * @param height 
  */ 
 public void setImageWidthAndHeight(int width, int height) { 
  imgWidth = width; 
  imgHeight = height; 
  RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams( 
    (int) imgWidth, (int) imgHeight); 
  imageView.setLayoutParams(layoutParams); 
 } 
 
 public boolean onTouchEvent(MotionEvent event) { 
  Log.w(TAG, "onTouchEvent :" + event.getAction()); 
  // 当该View放置在ScrollView里面时，会与父控件Touch事件冲突，所以touch该控件区域时，父控件不可用 
  if (event.getAction() == MotionEvent.ACTION_UP) { 
   getParent().requestDisallowInterceptTouchEvent(false); 
  } else { 
   getParent().requestDisallowInterceptTouchEvent(true);// true表示父类的不可用; 
  } 
  switch (event.getAction() & MotionEvent.ACTION_MASK) { 
  // 手指压下屏幕 
  case MotionEvent.ACTION_DOWN: 
   if (isBacking) { 
    return super.onTouchEvent(event); 
   } 
   int[] location = new int[2]; 
   imageView.getLocationInWindow(location); 
   if (location[1] >= 0) { 
    mode = MODE_DRAG; 
    // 记录ImageView当前的移动位置 
    currentMatrix.set(imageView.getImageMatrix()); 
    startPoint.set(event.getX(), event.getY()); 
    startRawY = event.getRawY(); 
    Log.w(TAG, "onTouchEvent startRawY:" + startRawY); 
   } 
   break; 
  // 手指在屏幕上移动，改事件会被不断触发 
  case MotionEvent.ACTION_MOVE: 
   // 拖拉图片 
   if (mode == MODE_DRAG) { 
//    float dx = event.getX() - startPoint.x; // 得到x轴的移动距离 
    float dy = event.getY() - startPoint.y; // 得到y轴的移动距离 
    // 在没有移动之前的位置上进行移动 
    if (dy > 0) { 
     matrix.set(currentMatrix); 
     Log.w(TAG, "onTouchEvent dy:" + dy); 
     scale = ((dy / (displayHeight - startRawY) * (displayHeight - imgHeight)) + imgHeight) 
       / imgHeight; // 得到缩放倍数，当手指移动到屏幕底部时，图片也达到屏幕底部 
     Log.w(TAG, "onTouchEvent scale:" + scale); 
     
     scaleY = dy; 
     RelativeLayout.LayoutParams relativeLayout = new RelativeLayout.LayoutParams( 
       (int) (scale * imgWidth), (int) (scale * imgHeight)); 
     imageView.setLayoutParams(relativeLayout); 
     matrix.postScale(scale, scale, imgWidth / 2, 0); 
     imageView.setImageMatrix(matrix); 
    } 
   } 
   break; 
  // 手指离开屏幕 
  case MotionEvent.ACTION_UP: 
   // 当触点离开屏幕，图片还原 
   mHandler.sendEmptyMessage(BACK_SCALE); 
  case MotionEvent.ACTION_POINTER_UP: 
   // 当两个手指移动时，取消移动图片 
   mode = 0; 
   break; 
  } 
  // 设置的Touch监听事件 
  if (touchEventListener != null) { 
   touchEventListener.onTouchEvent(event); 
  } 
  return true; 
 } 
  
 /** 逐步回弹 */ 
 @SuppressLint("HandlerLeak") 
 private Handler mHandler = new Handler() { 
  @Override 
  public void handleMessage(Message msg) { 
   // TODO Auto-generated method stub 
   switch (msg.what) { 
   case BACK_SCALE: 
    scale = (scaleY / 2 + imgHeight) / (imgHeight);// 得到缩放倍数 
    if (scaleY > 0) { 
     isBacking = true; 
     matrix.set(currentMatrix); 
     RelativeLayout.LayoutParams relativeLayout = new RelativeLayout.LayoutParams( 
       (int) (scale * imgWidth), (int) (scale * imgHeight)); 
     imageView.setLayoutParams(relativeLayout); 
     matrix.postScale(scale, scale, imgWidth / 2, 0); 
     imageView.setImageMatrix(matrix); 
     scaleY = (float) (scaleY / 2 - 1); 
     mHandler.sendEmptyMessageDelayed(BACK_SCALE, 20);// 逐步回弹 
    } else { 
     scaleY = 0; 
     RelativeLayout.LayoutParams relativeLayout = new RelativeLayout.LayoutParams( 
       (int) imgWidth, (int) imgHeight); 
     imageView.setLayoutParams(relativeLayout); 
     matrix.set(defaultMatrix); 
     imageView.setImageMatrix(matrix); 
     isBacking = false; 
    } 
    if (backScaleListener != null) { 
     backScaleListener.onBackScale(); 
    } 
    break; 
   default: 
    break; 
   } 
   super.handleMessage(msg); 
  } 
 }; 
  
 public void setTouchEventListener(TouchEventListener touchEventListener) { 
  this.touchEventListener = touchEventListener; 
 } 
  
 public void setBackScaleListener(BackScaleListener backScaleListener) { 
  this.backScaleListener = backScaleListener; 
 } 
 
 /** Touch事件监听 */ 
 public interface TouchEventListener { 
  public void onTouchEvent(MotionEvent event); 
 } 
 /** 回弹事件监听 */ 
 public interface BackScaleListener { 
  public void onBackScale(); 
 } 
}

调用的Activity：

package com.example.dragimagescale; 
 
import com.example.dragimagescale.DragScaleImageView.BackScaleListener; 
import com.example.dragimagescale.DragScaleImageView.TouchEventListener; 
 
import android.app.Activity; 
import android.os.Bundle; 
import android.view.MotionEvent; 
 
public class MainActivity extends Activity { 
 
  
 DragScaleImageView mDragScaleImageView; 
  
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
  super.onCreate(savedInstanceState); 
  setContentView(R.layout.activity_main); 
 
  mDragScaleImageView = (DragScaleImageView) findViewById(R.id.dragScaleImageView); 
  /** 自定义ImageView的宽高，若不设置则按图片宽高压缩至屏幕宽度 */ 
//  mDragScaleImageView.setImageWidthAndHeight(720, 300); 
  // Touch事件监听 
  mDragScaleImageView.setTouchEventListener(new TouchEventListener() { 
    
   @Override 
   public void onTouchEvent(MotionEvent event) { 
    // TODO Auto-generated method stub 
    // do something here 
   } 
  }); 
  // 回弹事件监听 
  mDragScaleImageView.setBackScaleListener(new BackScaleListener() { 
    
   @Override 
   public void onBackScale() { 
    // TODO Auto-generated method stub 
    // do something here 
   } 
  }); 
 } 
 
  
  
  
 
}

xml 布局文件：

下载：源码

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AndroidDragImageView实现下拉拖动图片放大效果

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