Android 多媒体开发学习之制作一个简单的画板

public class MainActivity extends Activity {

	private int TouchX;
	private int TouchY;
	private Paint paint;
	private Canvas canvas;
	Bitmap bitmapCopy;
	ImageView lView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        //1: 先创建一个画板的背景图片，这时候这图片需要修改，就需要创建该图片的副本
        Bitmap bitmapSrc = BitmapFactory.decodeResource(getResources(), R.drawable.bg);
        bitmapCopy = Bitmap.createBitmap(bitmapSrc.getWidth(), bitmapSrc.getHeight(), bitmapSrc.getConfig());
        
        paint = new Paint();
        canvas = new Canvas(bitmapCopy);
        canvas.drawBitmap(bitmapSrc, new Matrix(), paint);
        
        lView = (ImageView) findViewById(R.id.lv);
        lView.setImageBitmap(bitmapCopy);
        
        //2: 就需要监听手指的触摸事件
        lView.setOnTouchListener(new OnTouchListener() {
			
			@Override
			public boolean onTouch(View v, MotionEvent event) {
				//手指触摸分三种： 按下， 抬起，移动
				int action = event.getAction();
				switch (action) {
				case MotionEvent.ACTION_DOWN:
					//首先是按下，当按下时，需要记录第一次按下的位置
					TouchX = (int) event.getX();
					TouchY = (int) event.getY();
					break;
				case MotionEvent.ACTION_MOVE:
					//只要每次移动，都会产生移动事件的,得到当前的坐标
					int x = (int)event.getX();
					int y = (int)event.getY();
					//画线
					canvas.drawLine(TouchX, TouchY, x, y, paint);
					//更改下次绘制的起始坐标
					TouchX = x;
					TouchY = y;
					lView.setImageBitmap(bitmapCopy);
					break;
				case MotionEvent.ACTION_UP:
	
					break;
				
				}
				//true：告诉系统，这个触摸事件由我来处理
				//false：告诉系统，这个触摸事件我不处理，这时系统会把触摸事件传递给imageview的父节点
				return true;
			}
		});
    
    }
    
    //设置画笔的颜色为红色
    public void red(View v)
    {
    	paint.setColor(Color.RED);
    }

    //设置画笔的颜色为绿色
    public void green(View v)
    {
    	paint.setColor(Color.GREEN);
    }
    
    //设置刷子的宽度
    public void brush(View v)
    {
    	paint.setStrokeWidth(7);
    }
    
    //保存
    public void save(View v)
    {
    	File file = new File("sdcard/tupian.png");
    	
    	FileOutputStream fStream = null;
    	try {
			fStream = new FileOutputStream(file);
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
    	
    	//保存为png格式，100代表最高质量
    	bitmapCopy.compress(CompressFormat.PNG, 100, fStream);
    }
}