MultiTouchImageView.java

package eoc.studio.voicecard.animation;

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.AttributeSet;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;

/**
 * @see https://github.com/judepereira/android-multitouch
 * 
 */
public class MultiTouchImageView extends ImageView
{
	// these matrices will be used to move and zoom image
	private Matrix matrix = new Matrix();
	private Matrix savedMatrix = new Matrix();
	// we can be in one of these 3 states
	private static final int NONE = 0;
	private static final int DRAG = 1;
	private static final int ZOOM = 2;
	private int mode = NONE;
	// remember some things for zooming
	private PointF start = new PointF();
	private PointF mid = new PointF();
	private float oldDist = 1f;
	private float d = 0f;
	private float newRot = 0f;
	private float[] lastEvent = null;
	private OnTouchListener mClientTouchListener = null;
	private OnTouchListener mOwnTouchListener = new OnTouchListener()
	{
		@Override
		public boolean onTouch(View v, MotionEvent event)
		{
			// handle touch events here
			ImageView view = (ImageView) v;
			switch (event.getAction() & MotionEvent.ACTION_MASK)
			{
			case MotionEvent.ACTION_DOWN:
				savedMatrix.set(matrix);
				start.set(event.getX(), event.getY());
				mode = DRAG;
				lastEvent = null;
				break;
			case MotionEvent.ACTION_POINTER_DOWN:
				oldDist = spacing(event);
				if (oldDist > 10f)
				{
					savedMatrix.set(matrix);
					midPoint(mid, event);
					mode = ZOOM;
				}
				lastEvent = new float[4];
				lastEvent[0] = event.getX(0);
				lastEvent[1] = event.getX(1);
				lastEvent[2] = event.getY(0);
				lastEvent[3] = event.getY(1);
				d = rotation(event);
				break;
			case MotionEvent.ACTION_UP:
			case MotionEvent.ACTION_POINTER_UP:
				mode = NONE;
				lastEvent = null;
				break;
			case MotionEvent.ACTION_MOVE:
				if (mode == DRAG)
				{
					matrix.set(savedMatrix);
					float dx = event.getX() - start.x;
					float dy = event.getY() - start.y;
					matrix.postTranslate(dx, dy);
				}
				else if (mode == ZOOM)
				{
					float newDist = spacing(event);
					if (newDist > 10f)
					{
						matrix.set(savedMatrix);
						float scale = (newDist / oldDist);
						matrix.postScale(scale, scale, mid.x, mid.y);
					}
//					if (lastEvent != null && event.getPointerCount() == 3)
//					{
//						newRot = rotation(event);
//						float r = newRot - d;
//						float[] values = new float[9];
//						matrix.getValues(values);
//						float tx = values[2];
//						float ty = values[5];
//						float sx = values[0];
//						float xc = (view.getWidth() / 2) * sx;
//						float yc = (view.getHeight() / 2) * sx;
//						matrix.postRotate(r, tx + xc, ty + yc);
//					}
				}
				break;
			}
			view.setImageMatrix(matrix);
			if (mClientTouchListener != null)
			{
				mClientTouchListener.onTouch(v, event);
			}
			return true;
		}
	};

	public MultiTouchImageView(Context context, AttributeSet attrs)
	{
		super(context, attrs);
		this.setScaleType(ScaleType.MATRIX);
		super.setOnTouchListener(mOwnTouchListener);
	}

	@Override
	public void setOnTouchListener(OnTouchListener l)
	{
		mClientTouchListener = l;
	}

	/**
	 * Determine the space between the first two fingers
	 */
	private float spacing(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);
	}

	/**
	 * Calculate the mid point of the first two fingers
	 */
	private void midPoint(PointF point, MotionEvent event)
	{
		float x = event.getX(0) + event.getX(1);
		float y = event.getY(0) + event.getY(1);
		point.set(x / 2, y / 2);
	}

	/**
	 * Calculate the degree to be rotated by.
	 * 
	 * @param event
	 * @return Degrees
	 */
	private float rotation(MotionEvent event)
	{
		double delta_x = (event.getX(0) - event.getX(1));
		double delta_y = (event.getY(0) - event.getY(1));
		double radians = Math.atan2(delta_y, delta_x);
		return (float) Math.toDegrees(radians);
	}
}