android 大图片拖拽缩放

public class SpacePageActivity extends Activity {

	private LinearLayout linnerLayout_spacepage;
	private RelativeLayout relativeLayout_spacepage;
	private Button btn_spacepage_back;
	private Button btn_spacepage_save;
	private static Boolean isTrue=false;
	
	private static  String IMAGE_MIME_TYPE ;

	private ImageView image_spacePage;
	private ProgressDialog dialog;
	private Bitmap bitmap;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		requestWindowFeature(Window.FEATURE_NO_TITLE);//隐藏标题  
		setContentView(R.layout.spacepage);
		setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);   
		initHead();
	
        if(isNetworkAvailable()){
		image_spacePage=(ImageView) findViewById(R.id.image_spacepage);
		btn_spacepage_save=(Button) findViewById(R.id.btn_spacepage_save);
		image_spacePage.setOnTouchListener(new MulitPointTouchListener(image_spacePage));
		image_spacePage.setScaleType(ScaleType.CENTER_INSIDE);
		
		//加载成功
		String urls="http://epaper.yzdsb.com.cn/201201/04/yz2104_7.jpg";
		bitmap=returnBitMap(urls);
		if(null!=bitmap){
		 image_spacePage.setImageBitmap(bitmap);
		}
		
        }
    } 
	

	public Bitmap returnBitMap(String url) {  
		
		 if(null==url || "".equals(url)){
			 return null;
		 }
		   URL myFileUrl = null;   
		   Bitmap bitmap = null;   
		   try {   
		    myFileUrl = new URL(url);   
		   } catch (MalformedURLException e) {   
		    e.printStackTrace();   
		   }   
		   try {   
		    HttpURLConnection conn = (HttpURLConnection) myFileUrl.openConnection();
		    conn.setConnectTimeout(2000);
		    conn.setDoInput(true);   
		    conn.connect();   
		    InputStream is = conn.getInputStream();   
		    bitmap = BitmapFactory.decodeStream(is);   
		    is.close();   
		   } catch (IOException e) {   
		    e.printStackTrace();   
		   }   
		   
		   
		   
		   return bitmap;   
		} 
	public class MulitPointTouchListener implements OnTouchListener {    
		  
	    Matrix matrix = new Matrix();    
	    Matrix savedMatrix = new Matrix();    
	  
	    public ImageView image;    
	    static final int NONE = 0;    
	    static final int DRAG = 1;    
	    static final int ZOOM = 2;    
	    int mode = NONE;    
	  
	    PointF start = new PointF();    
	    PointF mid = new PointF();    
	    float oldDist = 1f;    
	  
	  
	    public MulitPointTouchListener(ImageView image) {    
	        super();    
	        this.image = image;    
	    }    
	  
	    @Override    
	    public boolean onTouch(View v, MotionEvent event) {    
	        this.image.setScaleType(ScaleType.MATRIX);    
	  
	        ImageView view = (ImageView) v;    
//	      dumpEvent(event);    
	  
	        switch (event.getAction() & MotionEvent.ACTION_MASK) {  
	          
	        case MotionEvent.ACTION_DOWN:    
	  
	            Log.w("FLAG", "ACTION_DOWN");  
	            matrix.set(view.getImageMatrix());    
	            savedMatrix.set(matrix);    
	            start.set(event.getX(), event.getY());    
	            mode = DRAG;    
	            break;    
	        case MotionEvent.ACTION_POINTER_DOWN:    
	            Log.w("FLAG", "ACTION_POINTER_DOWN");  
	            oldDist = spacing(event);    
	            if (oldDist > 10f) {    
	                savedMatrix.set(matrix);    
	                midPoint(mid, event);    
	                mode = ZOOM;    
	            }    
	            break;    
	        case MotionEvent.ACTION_UP:    
	            Log.w("FLAG", "ACTION_UP");  
	        case MotionEvent.ACTION_POINTER_UP:    
	            Log.w("FLAG", "ACTION_POINTER_UP");  
	            mode = NONE;    
	            break;    
	        case MotionEvent.ACTION_MOVE:    
	            Log.w("FLAG", "ACTION_MOVE");  
	            if (mode == DRAG) {    
	                matrix.set(savedMatrix);    
	                matrix.postTranslate(event.getX() - start.x, event.getY()    
	                        - start.y);    
	            } else if (mode == ZOOM) {    
	                float newDist = spacing(event);    
	                if (newDist > 10f) {    
	                    matrix.set(savedMatrix);    
	                    float scale = newDist / oldDist;    
	                    matrix.postScale(scale, scale, mid.x, mid.y);    
	                }    
	            }    
	            break;    
	        }    
	  
	        view.setImageMatrix(matrix);    
	        return true;  
	    }    
	  
	      
	    private float spacing(MotionEvent event) {    
	        float x = event.getX(0) - event.getX(1);    
	        float y = event.getY(0) - event.getY(1);    
	        return FloatMath.sqrt(x * x + y * y);    
	    }    
	  
	    private void midPoint(PointF point, MotionEvent event) {    
	        float x = event.getX(0) + event.getX(1);    
	        float y = event.getY(0) + event.getY(1);    
	        point.set(x / 2, y / 2);    
	    }    
	}   
	private void initHead() {
		linnerLayout_spacepage = (LinearLayout) findViewById(R.id.linnerLayout_spacepage);
		relativeLayout_spacepage=(RelativeLayout) findViewById(R.id.relativeLayout_spacepage);
		btn_spacepage_back = (Button) findViewById(R.id.btn_spacepage_back);
		btn_spacepage_back.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				
				finish();
			}
		});
		btn_spacepage_save = (Button) findViewById(R.id.btn_spacepage_save);
		
	}
	protected boolean isNetworkAvailable() {
		ConnectivityManager connectivity = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
		if (connectivity == null) {
			Log.i("NetWorkState", "Unavailabel");
			return false;
		} else {
			NetworkInfo[] info = connectivity.getAllNetworkInfo();
			if (info != null) {
				for (int i = 0; i < info.length; i++) {
					if (info[i].getState() == NetworkInfo.State.CONNECTED) {
						Log.i("NetWorkState", "Availabel");
						return true;
					}
				}
			}
		}
		return false;
	}
   @Override
protected void onStop() {
	// TODO Auto-generated method stub
	   if(bitmap!=null){
			if(!bitmap.isRecycled()){
				bitmap.recycle();   //回收图片所占的内存
				bitmap=null;
		         System.gc();  //提醒系统及时回收
		 }
		}
	super.onStop();
}
	@Override
	protected void onDestroy() {
		// TODO Auto-generated method stub
		super.onDestroy();
		if(bitmap!=null){
		if(!bitmap.isRecycled()){
			bitmap.recycle();   //回收图片所占的内存
			bitmap=null;
	         System.gc();  //提醒系统及时回收
	 }
		}
	}
}