Created
March 29, 2014 00:06
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Pinch-zoomable Android frame layout
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| package au.id.alexn; | |
| import android.content.Context; | |
| import android.util.AttributeSet; | |
| import android.util.Log; | |
| import android.view.MotionEvent; | |
| import android.view.ScaleGestureDetector; | |
| import android.view.View; | |
| import android.widget.FrameLayout; | |
| /** | |
| * Layout that provides pinch-zooming of content. This view should have exactly one child | |
| * view containing the content. | |
| */ | |
| public class ZoomLayout extends FrameLayout implements ScaleGestureDetector.OnScaleGestureListener { | |
| private enum Mode { | |
| NONE, | |
| DRAG, | |
| ZOOM | |
| } | |
| private static final String TAG = "ZoomLayout"; | |
| private static final float MIN_ZOOM = 1.0f; | |
| private static final float MAX_ZOOM = 4.0f; | |
| private Mode mode = Mode.NONE; | |
| private float scale = 1.0f; | |
| private float lastScaleFactor = 0f; | |
| // Where the finger first touches the screen | |
| private float startX = 0f; | |
| private float startY = 0f; | |
| // How much to translate the canvas | |
| private float dx = 0f; | |
| private float dy = 0f; | |
| private float prevDx = 0f; | |
| private float prevDy = 0f; | |
| public ZoomLayout(Context context) { | |
| super(context); | |
| init(context); | |
| } | |
| public ZoomLayout(Context context, AttributeSet attrs) { | |
| super(context, attrs); | |
| init(context); | |
| } | |
| public ZoomLayout(Context context, AttributeSet attrs, int defStyle) { | |
| super(context, attrs, defStyle); | |
| init(context); | |
| } | |
| private void init(Context context) { | |
| final ScaleGestureDetector scaleDetector = new ScaleGestureDetector(context, this); | |
| this.setOnTouchListener(new View.OnTouchListener() { | |
| @Override | |
| public boolean onTouch(View view, MotionEvent motionEvent) { | |
| switch (motionEvent.getAction() & MotionEvent.ACTION_MASK) { | |
| case MotionEvent.ACTION_DOWN: | |
| Log.i(TAG, "DOWN"); | |
| if (scale > MIN_ZOOM) { | |
| mode = Mode.DRAG; | |
| startX = motionEvent.getX() - prevDx; | |
| startY = motionEvent.getY() - prevDy; | |
| } | |
| break; | |
| case MotionEvent.ACTION_MOVE: | |
| if (mode == Mode.DRAG) { | |
| dx = motionEvent.getX() - startX; | |
| dy = motionEvent.getY() - startY; | |
| } | |
| break; | |
| case MotionEvent.ACTION_POINTER_DOWN: | |
| mode = Mode.ZOOM; | |
| break; | |
| case MotionEvent.ACTION_POINTER_UP: | |
| mode = Mode.DRAG; | |
| break; | |
| case MotionEvent.ACTION_UP: | |
| Log.i(TAG, "UP"); | |
| mode = Mode.NONE; | |
| prevDx = dx; | |
| prevDy = dy; | |
| break; | |
| } | |
| scaleDetector.onTouchEvent(motionEvent); | |
| if ((mode == Mode.DRAG && scale >= MIN_ZOOM) || mode == Mode.ZOOM) { | |
| getParent().requestDisallowInterceptTouchEvent(true); | |
| float maxDx = (child().getWidth() - (child().getWidth() / scale)) / 2 * scale; | |
| float maxDy = (child().getHeight() - (child().getHeight() / scale))/ 2 * scale; | |
| dx = Math.min(Math.max(dx, -maxDx), maxDx); | |
| dy = Math.min(Math.max(dy, -maxDy), maxDy); | |
| Log.i(TAG, "Width: " + child().getWidth() + ", scale " + scale + ", dx " + dx | |
| + ", max " + maxDx); | |
| applyScaleAndTranslation(); | |
| } | |
| return true; | |
| } | |
| }); | |
| } | |
| // ScaleGestureDetector | |
| @Override | |
| public boolean onScaleBegin(ScaleGestureDetector scaleDetector) { | |
| Log.i(TAG, "onScaleBegin"); | |
| return true; | |
| } | |
| @Override | |
| public boolean onScale(ScaleGestureDetector scaleDetector) { | |
| float scaleFactor = scaleDetector.getScaleFactor(); | |
| Log.i(TAG, "onScale" + scaleFactor); | |
| if (lastScaleFactor == 0 || (Math.signum(scaleFactor) == Math.signum(lastScaleFactor))) { | |
| scale *= scaleFactor; | |
| scale = Math.max(MIN_ZOOM, Math.min(scale, MAX_ZOOM)); | |
| lastScaleFactor = scaleFactor; | |
| } else { | |
| lastScaleFactor = 0; | |
| } | |
| return true; | |
| } | |
| @Override | |
| public void onScaleEnd(ScaleGestureDetector scaleDetector) { | |
| Log.i(TAG, "onScaleEnd"); | |
| } | |
| private void applyScaleAndTranslation() { | |
| child().setScaleX(scale); | |
| child().setScaleY(scale); | |
| child().setTranslationX(dx); | |
| child().setTranslationY(dy); | |
| } | |
| private View child() { | |
| return getChildAt(0); | |
| } | |
| } |
Hi how can we achieve the focus zoom in this code? I mean when ever we zoom the image it always zoom from center. If we want to zoom and see a specific part of image it doesn't work. I try making use of "getFocusX() & getFocusY()" but it is still not zooming on the focused position but always to centre.
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How can we reset the zoom?