CustomVIew(MyView)에서 TouchEvent(Move, Zoom in/out)

처음에 직접 하다가 zoom에서 막혔는데,

stackover flow보니까 잘 설명해놓은게 있네요 ㅎㅎ

영어만 있길래 한글로 옮겼습니다.

MainActivity

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(new TouchExampleView(this,null,0));
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}

TouchExampleView

public class TouchExampleView extends View {
	private Drawable mIcon;
	private float mPosX;
	private float mPosY;

	private float mLastTouchX;
	private float mLastTouchY;

	private static final int INVALID_POINTER_ID = -1;
	private ScaleGestureDetector mScaleDetector;
	private float mScaleFactor = 1.f;

	// The ‘active pointer’ is the one currently moving our object.
	private int mActivePointerId = INVALID_POINTER_ID;

	public TouchExampleView(Context context) {
		this(context, null, 0);
	}

	public TouchExampleView(Context context, AttributeSet attrs) {
		this(context, attrs, 0);
	}

	public TouchExampleView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		mIcon = context.getResources().getDrawable(R.drawable.ic_launcher);
		mIcon.setBounds(0, 0, mIcon.getIntrinsicWidth(),
				mIcon.getIntrinsicHeight());
		mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
	}

	@Override
	public void onDraw(Canvas canvas) {
		super.onDraw(canvas);

		canvas.save();
	    canvas.translate(mPosX, mPosY);
	    canvas.scale(mScaleFactor, mScaleFactor);
	    mIcon.draw(canvas);
	    canvas.restore();
	}

	@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;
	    }
	    }
	    
	    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;
		}
	}
}