Two finger touch scaling

lib/src/main/java/com/soundcloud/android/crop/CropImageView.java

@@ -2,8 +2,11 @@
 
 import android.content.Context;
 import android.graphics.Canvas;
+import android.graphics.PointF;
 import android.graphics.Rect;
+import android.os.Handler;
 import android.util.AttributeSet;
+import android.util.FloatMath;
 import android.view.MotionEvent;
 
 import java.util.ArrayList;
@@ -14,6 +17,26 @@ public class CropImageView extends ImageViewTouchBase {
     HighlightView motionHighlightView;
     Context context;
 
+    private static enum TouchState{
+        NONE,
+        SINGLE,
+        WAITING,
+        MULTI
+    };
+    private TouchState touchState = TouchState.NONE;
+    private Runnable enterSingleTouchHandler = new Runnable() {
+        @Override
+        public void run() {
+            touchState = TouchState.SINGLE;
+            onSingleTouchEvent(blockingEvent);
+        }
+    };
+
+    private MotionEvent blockingEvent;
+    private static final int waitingMillis = 70;   // 30ms is enough in most case
+    private Handler mHandler = new Handler();
+    private static float oldFingerDis = 0f;     // Finger's distance last zoom.
+
     private float lastX;
     private float lastY;
     private int motionEdge;
@@ -91,6 +114,104 @@ public boolean onTouchEvent(MotionEvent event) {
             return false;
         }
 
+        // Dispatch event
+        boolean blockEvent = false;
+        switch (event.getAction() & MotionEvent.ACTION_MASK) {
+            case MotionEvent.ACTION_DOWN:
+                // Fist touch point detected
+                // waiting for second point, or tiger singer touch event after a short period of time
+                touchState = TouchState.WAITING;
+                blockingEvent = MotionEvent.obtain(event);
+                blockEvent = true;
+                mHandler.postDelayed(enterSingleTouchHandler, waitingMillis);
+                break;
+            case MotionEvent.ACTION_POINTER_DOWN:
+                // Second or more touch point detected
+                // If is waiting, then it must be multi-touch event
+                if (touchState == TouchState.WAITING) {
+                    mHandler.removeCallbacks(enterSingleTouchHandler);
+                    touchState = TouchState.MULTI;
+                    // Send blocking event now
+                    onMultiTouchEvent(blockingEvent);
+                }
+                break;
+            case MotionEvent.ACTION_UP:
+                if (touchState == TouchState.WAITING) {
+                    mHandler.removeCallbacks(enterSingleTouchHandler);
+                    onSingleTouchEvent(blockingEvent);
+                    touchState = TouchState.SINGLE;
+                }
+                break;
+            case MotionEvent.ACTION_MOVE:
+                if (touchState == TouchState.WAITING) {
+                    blockEvent = true;
+                }
+                break;
+        }
+
+        if (!blockEvent) {
+            switch (touchState) {
+                case SINGLE:
+                    return onSingleTouchEvent(event);
+                case MULTI:
+                    return onMultiTouchEvent(event);
+            }
+        }
+
+        if (event.getAction() == MotionEvent.ACTION_UP) {
+            touchState = TouchState.NONE;
+        }
+        return true;
+    }
+
+    private static float getTwoFingerDis(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 static PointF getTwoFingerMiddle(MotionEvent event) {
+        if (event.getPointerCount() < 2) {
+            return new PointF(event.getX(), event.getY());
+        }
+
+        float x = (event.getX(0) + event.getX(1)) / 2f;
+        float y = (event.getY(0) + event.getY(1)) / 2f;
+        return new PointF(x, y);
+    }
+
+    private boolean onMultiTouchEvent(MotionEvent event) {
+        if (event.getPointerCount() < 2) {
+            return true;
+        }
+        switch (event.getAction() & MotionEvent.ACTION_MASK) {
+            case MotionEvent.ACTION_POINTER_DOWN:
+                oldFingerDis = getTwoFingerDis(event);
+                break;
+            case MotionEvent.ACTION_MOVE:
+                tryZoom(event);
+                break;
+
+        }
+        return true;
+    }
+
+    private boolean tryZoom(MotionEvent event) {
+        float curD = getTwoFingerDis(event);
+        PointF curM = getTwoFingerMiddle(event);
+
+        float shake = 5.0f;
+        if (Math.abs(curD - oldFingerDis) > shake) {
+            float scale = curD / oldFingerDis;
+            zoomTo(getScale() * scale, curM.x, curM.y);
+            oldFingerDis = curD;
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    private boolean onSingleTouchEvent(MotionEvent event) {
         switch (event.getAction()) {
         case MotionEvent.ACTION_DOWN:
             for (HighlightView hv : highlightViews) {
@@ -134,6 +255,7 @@ public boolean onTouchEvent(MotionEvent event) {
             // the user to move the image around. This call to center puts
             // it back to the normalized location (with false meaning don't
             // animate).
+            // Now it can zoom :)
             if (getScale() == 1F) {
                 center(true, true);
             }