Paint类（画笔）

<?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
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FrameLayout ll = (FrameLayout) findViewById(R.id.frameLayout1);
ll.addView(new MyView(this));
}

public class MyView extends View {

public MyView(Context context) {
super(context);
}

@Override
protected void onDraw(Canvas canvas) {
Paint paint = new Paint(); // 定义一个默认的画笔
// 线性渐变
Shader shader = new LinearGradient(0, 0, 50, 50, Color.RED,
Color.GREEN, Shader.TileMode.MIRROR);
paint.setShader(shader); // 为画笔设置渐变器
canvas.drawRect(10, 70, 100, 150, paint); // 绘制矩形
// 径向渐变
shader = new RadialGradient(160, 110, 50, Color.RED, Color.GREEN,
Shader.TileMode.MIRROR);
paint.setShader(shader); // 为画笔设置渐变器
canvas.drawRect(115, 70, 205, 150, paint); // 绘制矩形
// 角度渐变
shader = new SweepGradient(265, 110, new int[] { Color.RED,
Color.GREEN, Color.BLUE }, null);
paint.setShader(shader);
canvas.drawRect(220, 70, 310, 150, paint); // 绘制矩形

super.onDraw(canvas);
}

}
}