ScaleDetectorActivity.java

package com.google.mcommerce.sample.android.chapter08.gestures;

// This file is MainActivity.java
import android.app.Activity;
import android.graphics.Matrix;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.widget.ImageView;

import com.google.mcommerce.sample.android.R;

public class ScaleDetectorActivity extends Activity {
	private static final String TAG = "ScaleDetector";
	private ImageView image;
	private ScaleGestureDetector mScaleDetector;
	private float mScaleFactor = 1f;
	private Matrix mMatrix = new Matrix();

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.c08_scale_detector_layout);

		image = (ImageView) findViewById(R.id.image);
		mScaleDetector = new ScaleGestureDetector(this, new ScaleListener());
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		Log.v(TAG, "in onTouchEvent");
		// Give all events to ScaleGestureDetector
		mScaleDetector.onTouchEvent(ev);

		return true;
	}

	private class ScaleListener extends
			ScaleGestureDetector.SimpleOnScaleGestureListener {
		@Override
		public boolean onScale(ScaleGestureDetector detector) {
			mScaleFactor *= detector.getScaleFactor();

			// Make sure we don't get too small or too big
			mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 5.0f));

			Log.v(TAG, "in onScale, scale factor = " + mScaleFactor);
			mMatrix.setScale(mScaleFactor, mScaleFactor);

			image.setImageMatrix(mMatrix);
			image.invalidate();
			return true;
		}
	}
}