Android DragImageView实现下拉拖动图片放大效果

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(); 
} 
} 

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 
} 
}); 
} 
} 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:tools="http://schemas.android.com/tools" 
xmlns:dragscaleimageview="http://schemas.android.com/apk/res/com.example.dragimagescale" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:background="#ffffff"   
<com.example.dragimagescale.DragScaleImageView 
android:id="@+id/dragScaleImageView" 
android:layout_width="match_parent"   
android:layout_height="wrap_content" 
dragscaleimageview:scale_image="@drawable/image" 
</com.example.dragimagescale.DragScaleImageView  
</RelativeLayout