touchpaint.java

Google s android SDK

/* 
 * Copyright (C) 2007 Google Inc.
 *
 * 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.google.android.samples.graphics;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;

//Need the following import to get access to the app resources, since this
//class is in a sub-package.


/**
 * Demonstrates the handling of touch screen events to implement a simple
 * painting app.
 */
public class TouchPaint extends Activity {    
    @Override
    protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(new MyView(this));
    }
    
    public class MyView extends View {
        Bitmap mBitmap;
        Canvas mCanvas;
        private final Rect mRect = new Rect();
        private final Paint mPaint;
        private boolean mCurDown;
        private int mCurX;
        private int mCurY;
        private float mCurPressure;
        private float mCurSize;
        private int mCurWidth;
        
        public MyView(Context c) {
            super(c);
            mPaint = new Paint();
            mPaint.setAntiAlias(true);
            mPaint.setARGB(255, 255, 255, 255);
        }

        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            int curW = mBitmap != null ? mBitmap.width() : 0;
            int curH = mBitmap != null ? mBitmap.height() : 0;
            if (curW >= w && curH >= h) {
                return;
            }
            
            if (curW < w) curW = w;
            if (curH < h) curH = h;
            
            Bitmap newBitmap = Bitmap.createBitmap(curW, curH, false);
            Canvas newCanvas = new Canvas();
            newCanvas.setDevice(newBitmap);
            if (mBitmap != null) {
                newCanvas.drawBitmap(mBitmap, 0, 0, null);
            }
            mBitmap = newBitmap;
            mCanvas = newCanvas;
        }
        
        @Override
        protected void onDraw(Canvas canvas) {
            if (mBitmap != null) {
                canvas.drawBitmap(mBitmap, 0, 0, null);
            }
        }

        @Override
        public boolean onMotionEvent(MotionEvent event) {
            int action = event.getAction();
            mCurDown = action == MotionEvent.ACTION_DOWN
                    || action == MotionEvent.ACTION_MOVE;
            mCurX = (int)event.getX();
            mCurY = (int)event.getY();
            mCurPressure = event.getPressure();
            mCurSize = event.getSize();
            mCurWidth = (int)(mCurSize*(getWidth()/3));
            if (mCurWidth < 1) mCurWidth = 1;
            if (mCurDown && mBitmap != null) {
                int pressureLevel = (int)(mCurPressure*255);
                mPaint.setARGB(pressureLevel, 255, 255, 255);
                mCanvas.drawCircle(mCurX, mCurY, mCurWidth, mPaint);
                mRect.set(mCurX-mCurWidth-2, mCurY-mCurWidth-2,
                        mCurX+mCurWidth+2, mCurY+mCurWidth+2);
                invalidate(mRect);
            }
            return true;
        }
        
    }
}