这篇Android图片拖拽缩放也是我在项目中用到的，今天整理一下，将源码奉献给大家，希望对大家以后碰到相似的问题有帮助。
这篇就不做过多介绍了，直接上源码：
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 } } } }