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.
@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;
}
}
