这篇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。android 大图片拖拽缩放
这篇就不做过多介绍了，直接上源码：
1 public class SpacePageActivity extends Activity { 2 3 private LinearLayout linnerLayout_spacepage; 4 private RelativeLayout relativeLayout_spacepage; 5 private Button btn_spacepage_back; 6 private Button btn_spacepage_save; 7 private static Boolean isTrue=false; 8 9 private static String IMAGE_MIME_TYPE ; 10 11 private ImageView image_spacePage; 12 private ProgressDialog dialog; 13 private Bitmap bitmap; 14 @Override 15 protected void onCreate(Bundle savedInstanceState) { 16 // TODO Auto-generated method stub 17 super.onCreate(savedInstanceState); 18 requestWindowFeature(Window.FEATURE_NO_TITLE);//隐藏标题 19 setContentView(R.layout.spacepage); 20 setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE); 21 initHead(); 22 23 if(isNetworkAvailable()){ 24 image_spacePage=(ImageView) findViewById(R.id.image_spacepage); 25 btn_spacepage_save=(Button) findViewById(R.id.btn_spacepage_save); 26 image_spacePage.setOnTouchListener(new MulitPointTouchListener(image_spacePage)); 27 image_spacePage.setScaleType(ScaleType.CENTER_INSIDE); 28 29 //加载成功 何问起 30 String urls="http://epaper.yzdsb.com.cn/201201/04/yz2104_7.jpg"; 31 bitmap=returnBitMap(urls); 32 if(null!=bitmap){ 33 image_spacePage.setImageBitmap(bitmap); 34 } 35 36 } 37 } 38 39 40 public Bitmap returnBitMap(String url) { 41 42 if(null==url || "".equals(url)){ 43 return null; 44 } 45 URL myFileUrl = null; 46 Bitmap bitmap = null; 47 try { 48 myFileUrl = new URL(url); 49 } catch (MalformedURLException e) { 50 e.printStackTrace(); 51 } 52 try { 53 HttpURLConnection conn = (HttpURLConnection) myFileUrl.openConnection(); 54 conn.setConnectTimeout(2000); 55 conn.setDoInput(true); 56 conn.connect(); 57 InputStream is = conn.getInputStream(); 58 bitmap = BitmapFactory.decodeStream(is); 59 is.close(); 60 } catch (IOException e) { 61 e.printStackTrace(); 62 } 63 64 65 66 return bitmap; 67 } 68 // hovertree.com 69 70 public class MulitPointTouchListener implements OnTouchListener { 71 72 Matrix matrix = new Matrix(); 73 Matrix savedMatrix = new Matrix(); 74 75 public ImageView image; 76 static final int NONE = 0; 77 static final int DRAG = 1; 78 static final int ZOOM = 2; 79 int mode = NONE; 80 81 PointF start = new PointF(); 82 PointF mid = new PointF(); 83 float oldDist = 1f; 84 85 86 public MulitPointTouchListener(ImageView image) { 87 super(); 88 this.image = image; 89 } 90 91 @Override 92 public boolean onTouch(View v, MotionEvent event) { 93 this.image.setScaleType(ScaleType.MATRIX); 94 95 ImageView view = (ImageView) v; 96 // dumpEvent(event); 97 98 switch (event.getAction() & MotionEvent.ACTION_MASK) { 99 100 case MotionEvent.ACTION_DOWN: 101 102 Log.w("FLAG", "ACTION_DOWN"); 103 matrix.set(view.getImageMatrix()); 104 savedMatrix.set(matrix); 105 start.set(event.getX(), event.getY()); 106 mode = DRAG; 107 break; 108 case MotionEvent.ACTION_POINTER_DOWN: 109 Log.w("FLAG", "ACTION_POINTER_DOWN"); 110 oldDist = spacing(event); 111 if (oldDist > 10f) { 112 savedMatrix.set(matrix); 113 midPoint(mid, event); 114 mode = ZOOM; 115 } 116 break; 117 case MotionEvent.ACTION_UP: 118 Log.w("FLAG", "ACTION_UP"); 119 case MotionEvent.ACTION_POINTER_UP: 120 Log.w("FLAG", "ACTION_POINTER_UP"); 121 mode = NONE; 122 break; 123 case MotionEvent.ACTION_MOVE: 124 Log.w("FLAG", "ACTION_MOVE"); 125 if (mode == DRAG) { 126 matrix.set(savedMatrix); 127 matrix.postTranslate(event.getX() - start.x, event.getY() 128 - start.y); 129 } else if (mode == ZOOM) { 130 float newDist = spacing(event); 131 if (newDist > 10f) { 132 matrix.set(savedMatrix); 133 float scale = newDist / oldDist; 134 matrix.postScale(scale, scale, mid.x, mid.y); 135 } 136 } 137 break; 138 } 139 140 view.setImageMatrix(matrix); 141 return true; 142 } 143 144 145 private float spacing(MotionEvent event) { 146 float x = event.getX(0) - event.getX(1); 147 float y = event.getY(0) - event.getY(1); 148 return FloatMath.sqrt(x * x + y * y); 149 } 150 151 private void midPoint(PointF point, MotionEvent event) { 152 float x = event.getX(0) + event.getX(1); 153 float y = event.getY(0) + event.getY(1); 154 point.set(x / 2, y / 2); 155 } 156 } 157 private void initHead() { 158 linnerLayout_spacepage = (LinearLayout) findViewById(R.id.linnerLayout_spacepage); 159 relativeLayout_spacepage=(RelativeLayout) findViewById(R.id.relativeLayout_spacepage); 160 btn_spacepage_back = (Button) findViewById(R.id.btn_spacepage_back); 161 btn_spacepage_back.setOnClickListener(new OnClickListener() { 162 163 @Override 164 public void onClick(View v) { 165 // TODO Auto-generated method stub 166 167 finish(); 168 } 169 }); 170 btn_spacepage_save = (Button) findViewById(R.id.btn_spacepage_save); 171 172 } 173 protected boolean isNetworkAvailable() { 174 ConnectivityManager connectivity = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE); 175 if (connectivity == null) { 176 Log.i("NetWorkState", "Unavailabel"); 177 return false; 178 } else { 179 NetworkInfo[] info = connectivity.getAllNetworkInfo(); 180 if (info != null) { 181 for (int i = 0; i < info.length; i++) { 182 if (info[i].getState() == NetworkInfo.State.CONNECTED) { 183 Log.i("NetWorkState", "Availabel"); 184 return true; 185 } 186 } 187 } 188 } 189 return false; 190 } 191 @Override 192 protected void onStop() { 193 // TODO Auto-generated method stub 194 if(bitmap!=null){ 195 if(!bitmap.isRecycled()){ 196 bitmap.recycle(); //回收图片所占的内存 197 bitmap=null; 198 System.gc(); //提醒系统及时回收 199 } 200 } 201 super.onStop(); 202 } 203 @Override 204 protected void onDestroy() { 205 // TODO Auto-generated method stub 206 super.onDestroy(); 207 if(bitmap!=null){ 208 if(!bitmap.isRecycled()){ 209 bitmap.recycle(); //回收图片所占的内存 210 bitmap=null; 211 System.gc(); //提醒系统及时回收 212 } 213 } 214 } 215 } 因为是大图片，在onDestroy的时候要recycle掉，这样系统才会定时回收掉，System.gc();是提醒系统回收，虽然java这种垃圾回收机制不用我们自己关心对象的回收，但是这也给android开发人员带来了不好的一面，如果系统回收不及时很可能就造成了内存溢出了。什么时候手机不担心内存使用了就好了。
运行一下看看效果：
