http://topic.csdn.net/u/20101127/00/d7cbe737-f9ef-4a19-ae0e-b61f7b447d5f.html

public class AndroidTest extends Activity {
    private LinearLayout layout;
    private LinearLayout.LayoutParams params1, params2;
    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        layout = (LinearLayout)findViewById(R.id.rootLayout);
        params1 = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
        params2 = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
        MyView myView1 = new MyView(this, 100, 100, 50);
        myView1.setColor(Color.MAGENTA);
        myView1.layout(50, 50, 150, 150);
        myView1.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                // TODO Auto-generated method stub
                setTitle("MyView");
            }
            
        });
        layout.addView(myView1, params1);
        
        MyView smallCircle = new MyView(this, 125, 200, 25);
        smallCircle.setColor(Color.GREEN);
        smallCircle.layout(100, 175, 150, 225);
        layout.addView(smallCircle, params2);
        
    }
    
    public class MyView extends View {
        private float m_cx;
        private float m_cy;
        private float m_radius;
        private Paint paint;
        
        MyView(Context context, float cx, float cy, float radius) {
            super(context);
            m_cx = cx;
            m_cy = cy;
            m_radius = radius;
            
            // 首先定义一个paint 
            paint = new Paint(); 
            
            // 绘制矩形区域-实心矩形 
            // 设置颜色 
            paint.setColor(Color.BLUE); 
            // 设置样式-填充 
            paint.setStyle(Style.FILL);
        }
        
        public void setColor(int color) {
            // 设置颜色 
            paint.setColor(color);
        }
        
        @Override
        protected void onDraw(Canvas canvas) {
            // TODO Auto-generated method stub
            super.onDraw(canvas);

            // draw circle
            canvas.drawCircle(m_cx, m_cy, m_radius, paint);
        }
        
    }
}