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POGet Canvas coordinates after scaling up/down or dragging in android
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copied!<p>I'm developing an application in which I'm pasting images, doing drawing and painting on canvas. This app can also Scale up/down the canvas or drag it to different location. My problem is: I can't get the correct canvas coordinates after scaling or dragging the canvas. I want to draw finger paint after the canvas is scaled or dragged but unable to retrieve the right place where i've touched..:( Also I'm new bee. Here is the code.</p> <pre><code>@Override public void onDraw(Canvas canvas) { super.onDraw(canvas); canvas.save(); //canvas.translate(mPosX, mPosY); canvas.scale(mScaleFactor, mScaleFactor, super.getWidth() * 0.5f, super.getHeight() * 0.5f); mIcon.draw(canvas); for (Path path : listPath) { canvas.drawPath(path, paint); } canvas.restore(); } public TouchExampleView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); } @Override public boolean onTouchEvent(MotionEvent ev) { // Let the ScaleGestureDetector inspect all events. mScaleDetector.onTouchEvent(ev); final int action = ev.getAction(); switch (action & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: { final float x = ev.getX(); final float y = ev.getY(); mLastTouchX = x; mLastTouchY = y; mActivePointerId = ev.getPointerId(0); break; } case MotionEvent.ACTION_MOVE: { final int pointerIndex = ev.findPointerIndex(mActivePointerId); final float x = ev.getX(pointerIndex); final float y = ev.getY(pointerIndex); // Only move if the ScaleGestureDetector isn't processing a gesture. if (!mScaleDetector.isInProgress()) { final float dx = x - mLastTouchX; final float dy = y - mLastTouchY; mPosX += dx; mPosY += dy; invalidate(); } mLastTouchX = x; mLastTouchY = y; break; } case MotionEvent.ACTION_UP: { mActivePointerId = INVALID_POINTER_ID; break; } case MotionEvent.ACTION_CANCEL: { mActivePointerId = INVALID_POINTER_ID; break; } case MotionEvent.ACTION_POINTER_UP: { final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; final int pointerId = ev.getPointerId(pointerIndex); if (pointerId == mActivePointerId) { // This was our active pointer going up. Choose a new // active pointer and adjust accordingly. final int newPointerIndex = pointerIndex == 0 ? 1 : 0; mLastTouchX = ev.getX(newPointerIndex); mLastTouchY = ev.getY(newPointerIndex); mActivePointerId = ev.getPointerId(newPointerIndex); } break; } } float objectNewX,objectNewY; if (mScaleFactor >= 1) { objectNewX = ev.getX() + (ev.getX() - super.getWidth() * 0.5f) * (mScaleFactor - 1); objectNewY = ev.getY() + (ev.getY() - super.getHeight() * 0.5f) * (mScaleFactor - 1); } else { objectNewX = ev.getX() - (ev.getX() - super.getWidth() * 0.5f) * (1 - mScaleFactor); objectNewY = ev.getY() - (ev.getY() - super.getHeight() * 0.5f) * (1 - mScaleFactor); } if (ev.getAction() == MotionEvent.ACTION_DOWN) { path = new Path(); path.moveTo(objectNewX,objectNewY); path.lineTo(objectNewX,objectNewY); } else if (ev.getAction() == MotionEvent.ACTION_MOVE) { path.lineTo(objectNewX,objectNewY); listPath.add(path); } else if (ev.getAction() == MotionEvent.ACTION_UP) { path.lineTo(objectNewX,objectNewY); listPath.add(path); } return true; } private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener { @Override public boolean onScale(ScaleGestureDetector detector) { mScaleFactor *= detector.getScaleFactor(); // Don't let the object get too small or too large. mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 5.0f)); invalidate(); return true; } } </code></pre>

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