Android中在屏幕上涂鸦的例子

这个例子，自定义了一个View，可以接受touch动作，然后在屏幕上即时的显示出touch的轨迹，类似于线条的涂鸦。这个例子主要是演示如何将onTouchEvent与draw配合起来使用。在这个基础上，可以做很多有用的程序。

import android.content.Context;  
import android.graphics.Canvas;  
import android.graphics.Color;  
import android.graphics.Paint;  
import android.graphics.Path;  
import android.graphics.Paint.Style;  
import android.view.MotionEvent;  
import android.view.View;  
/** 
 * Example for hand writing. 
 *  
 * @author http://blog.csdn.net/arui319 
 * @version 2010/09/07 
 *  
 */  
public class HandwritingView extends View {  
    private Paint paint = null;  
    private Path path = null;  
    public HandwritingView(Context context) {  
        super(context);  
        path = new Path();  
        paint = new Paint();  
        paint.setColor(Color.YELLOW);  
        paint.setStyle(Style.STROKE);  
        paint.setAntiAlias(true);  
        this.setBackgroundColor(Color.BLACK);  
    }  
    @Override  
    public boolean onTouchEvent(MotionEvent event) {  
        if (event.getAction() == MotionEvent.ACTION_DOWN) {  
            int x = (int) event.getX();  
            int y = (int) event.getY();  
            path.moveTo(x, y);  
            invalidate();  
            return true;  
        } else if (event.getAction() == MotionEvent.ACTION_MOVE) {  
            int x = (int) event.getX();  
            int y = (int) event.getY();  
            path.lineTo(x, y);  
            invalidate();  
            return true;  
        }  
        return super.onTouchEvent(event);  
    }  
    @Override  
    protected void onDraw(Canvas canvas) {  
        super.onDraw(canvas);  
        if (path != null) {  
            canvas.drawPath(path, paint);  
        }  
    }  
}