samples/CrossCompatibility/src/com/example/android/touchexample/TouchExampleView.java

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.example.android.touchexample;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

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

    private VersionedGestureDetector mDetector;
    private float mScaleFactor = 1.f;

    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.icon);
        mIcon.setBounds(0, 0, mIcon.getIntrinsicWidth(), mIcon.getIntrinsicHeight());

        mDetector = VersionedGestureDetector.newInstance(context, new GestureCallback());
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        mDetector.onTouchEvent(ev);
        return true;
    }

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

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

    private class GestureCallback implements VersionedGestureDetector.OnGestureListener {
        public void onDrag(float dx, float dy) {
            mPosX += dx;
            mPosY += dy;
            invalidate();
        }

        public void onScale(float scaleFactor) {
            mScaleFactor *= scaleFactor;

            // Don't let the object get too small or too large.
            mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 5.0f));

            invalidate();
        }
    }
}