首先画一个空心的矩形框，代码如下：

public class MainActivity extends Activity {    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);                ImageView image = (ImageView) findViewById(R.id.image);                Bitmap bitmap = Bitmap.createBitmap(800, 480, Config.ARGB_8888);        Canvas canvas = new Canvas(bitmap);        canvas.drawColor(Color.BLUE);        Rect rect = new Rect(0, 0, 800, 480);        Paint paint= new Paint();        paint.setStyle(Style.STROKE);        paint.setColor(Color.RED);        paint.setStrokeWidth(2);//这个地方改线宽,单位是像素canvas.drawRect(rect, paint);image.setImageBitmap(bitmap);    }    }

这时遇到的问题是画矩形框的线宽的单位是什么？

答案是像素。答案来源一方面是自己试，另一方面是来自以下链接：

http://stackoverflow.com/questions/4789806/what-unit-of-measure-does-paint-setstrokewidth-use