android 图片的浏览、缩放、拖动和自动居中示例

android OpenGL 知识汇总
http://www.eoeandroid.com/thread-203299-1-1.html

检测手机wifi的状态
http://www.eoeandroid.com/thread-203307-1-1.html

GridView + ViewFlipper布局界面，模仿“机锋市场”
http://www.eoeandroid.com/thread-203252-1-1.html

直接上代码吧！文中写了比较详细的注释。

/** * 图片浏览、缩放、拖动、自动居中 */  public class ImageTouch extends Activity implements OnTouchListener {      Matrix matrix = new Matrix();      Matrix savedMatrix = new Matrix();      DisplayMetrics dm;      ImageView imgView;      Bitmap bitmap;      float minScaleR;// 最小缩放比例      static final float MAX_SCALE = 4f;// 最大缩放比例      static final int NONE = 0;// 初始状态      static final int DRAG = 1;// 拖动      static final int ZOOM = 2;// 缩放      int mode = NONE;      PointF prev = new PointF();      PointF mid = new PointF();      float dist = 1f;        @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.main);          imgView = (ImageView) findViewById(R.id.imag);// 获取控件          // bitmap = BitmapFactory.decodeResource(getResources(),          // this.getIntent()          // .getExtras().getInt("IMG"));// 获取图片资源          bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.image);// 获取图片资源          imgView.setImageBitmap(bitmap);// 填充控件          imgView.setOnTouchListener(this);// 设置触屏监听          dm = new DisplayMetrics();          getWindowManager().getDefaultDisplay().getMetrics(dm);// 获取分辨率          minZoom();          center();          imgView.setImageMatrix(matrix);      }        /** * 触屏监听 */      public boolean onTouch(View v, MotionEvent event) {          switch (event.getAction() & MotionEvent.ACTION_MASK) { // 主点按下          case MotionEvent.ACTION_DOWN:              savedMatrix.set(matrix);              prev.set(event.getX(), event.getY());              mode = DRAG;              break; // 副点按下          case MotionEvent.ACTION_POINTER_DOWN:              dist = spacing(event); // 如果连续两点距离大于10，则判定为多点模式              if (spacing(event) > 10f) {                  savedMatrix.set(matrix);                  midPoint(mid, event);                  mode = ZOOM;              }              break;          case MotionEvent.ACTION_UP:          case MotionEvent.ACTION_POINTER_UP:              mode = NONE;              break;          case MotionEvent.ACTION_MOVE:              if (mode == DRAG) {                  matrix.set(savedMatrix);                  matrix.postTranslate(event.getX() - prev.x, event.getY()                          - prev.y);              } else if (mode == ZOOM) {                  float newDist = spacing(event);                  if (newDist > 10f) {                      matrix.set(savedMatrix);                      float tScale = newDist / dist;                      matrix.postScale(tScale, tScale, mid.x, mid.y);                  }              }              break;          }          imgView.setImageMatrix(matrix);          CheckView();          return true;      }        /** * 限制最大最小缩放比例，自动居中 */      private void CheckView() {          float p[] = new float[9];          matrix.getValues(p);          if (mode == ZOOM) {              if (p[0] < minScaleR) {                  matrix.setScale(minScaleR, minScaleR);              }              if (p[0] > MAX_SCALE) {                  matrix.set(savedMatrix);              }          }          center();      }        /** * 最小缩放比例，最大为100% */      private void minZoom() {          minScaleR = Math.min(                  (float) dm.widthPixels / (float) bitmap.getWidth(),                  (float) dm.heightPixels / (float) bitmap.getHeight());          if (minScaleR < 1.0) {              matrix.postScale(minScaleR, minScaleR);          }      }        private void center() {          center(true, true);      }        /** * 横向、纵向居中 */      protected void center(boolean horizontal, boolean vertical) {          Matrix m = new Matrix();          m.set(matrix);          RectF rect = new RectF(0, 0, bitmap.getWidth(), bitmap.getHeight());          m.mapRect(rect);          float height = rect.height();          float width = rect.width();          float deltaX = 0, deltaY = 0;          if (vertical) {              // 图片小于屏幕大小，则居中显示。大于屏幕，上方留空则往上移，下放留空则往下移              int screenHeight = dm.heightPixels;              if (height < screenHeight) {                  deltaY = (screenHeight - height) / 2 - rect.top;              } else if (rect.top > 0) {                  deltaY = -rect.top;              } else if (rect.bottom < screenHeight) {                  deltaY = imgView.getHeight() - rect.bottom;              }          }          if (horizontal) {              int screenWidth = dm.widthPixels;              if (width < screenWidth) {                  deltaX = (screenWidth - width) / 2 - rect.left;              } else if (rect.left > 0) {                  deltaX = -rect.left;              } else if (rect.right < screenWidth) {                  deltaX = screenWidth - rect.right;              }          }          matrix.postTranslate(deltaX, deltaY);      }        /** * 两点的距离 */      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);      }        /** * 两点的中点 */      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);      }  }

main.xml

<?xml version="1.0" encoding="utf-8"?>      <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"          android:layout_width="fill_parent" android:layout_height="fill_parent"          android:layout_gravity="center">          <ImageView android:id="@+id/imag" android:layout_width="fill_parent"              android:layout_height="fill_parent" android:layout_gravity="center"              android:scaleType="matrix">          </ImageView>      </FrameLayout>

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