Canvas类绘制几何图形

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/frameLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

</FrameLayout>

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FrameLayout ll = (FrameLayout)findViewById(R.id.frameLayout1);//获取布局文件中添加的帧布局管理器
ll.addView(new MyView(this));//将自定义的MyView视图添加到帧布局管理器中
}

public class MyView extends View{

public MyView(Context context) {
super(context);
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.WHITE);//制定画布的背景色为白色
Paint paint = new Paint();//创建采用默认设置的画笔
paint.setAntiAlias(true);//使用抗锯齿功能
paint.setStrokeWidth(3);//设置笔触的宽度
paint.setStyle(Style.STROKE);//设置填充样式为描边
paint.setColor(Color.BLUE);
canvas.drawCircle(50, 50, 30, paint);//绘制蓝色的圆形
paint.setColor(Color.YELLOW);
canvas.drawCircle(100, 50, 30, paint);//绘制黄色的圆形
paint.setColor(Color.BLACK);
canvas.drawCircle(150, 50, 30, paint);//绘制黑色的圆形
paint.setColor(Color.GREEN);
canvas.drawCircle(75, 90, 30, paint);//绘制绿色的圆形
paint.setColor(Color.RED);
canvas.drawCircle(125, 90, 30, paint);//绘制红色的圆形
super.onDraw(canvas);
}

}

}