public class Yidong2 extends AppCompatActivity {
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(new PointView(this));
 }
 
 public class PointView extends View {
  private int[] p1 = {0, 100, 200};  //存放弧度的數(shù)組
  //定義存放顏色的數(shù)組
  private int[] p2 = {Color.GREEN, Color.YELLOW, Color.RED};  
  Paint paint = new Paint();    //畫筆
  private float k;      //弧度變動(dòng)后的值
 
  //定義矩形，用戶確定描繪的餅狀圖位置
  private final RectF rectF = new RectF(100, 100, 800, 800);
 
  //定義
  public PointView(Context context) {
   super(context);
   paint.setStyle(Paint.Style.FILL);  //設(shè)置畫筆為填充
   paint.setStrokeWidth(10f);    //設(shè)置畫筆寬度
   paint.setAntiAlias(true);    //抗鋸齒
 
   //屬性動(dòng)畫
   ValueAnimator animator = ValueAnimator.ofFloat(0, 360);
   animator.setDuration(1000);    //設(shè)置動(dòng)畫時(shí)間
   animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
    @Override
    public void onAnimationUpdate(ValueAnimator animation) {
     k = (float) animation.getAnimatedValue(); //獲取變動(dòng)后的值
     invalidate();   //刷新布局
    }
   });
   animator.start(); //啟動(dòng)動(dòng)畫
  }
 
  @SuppressLint("DrawAllocation")
  @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
  @Override
  protected void onDraw(Canvas canvas) {
   super.onDraw(canvas);
   //這里做了不同顏色的范圍判斷，還可以進(jìn)行封裝，為了便于學(xué)習(xí)，就沒(méi)有再次封裝
   if (k < p1[1]) {
    shezhi(canvas, 0);
   } else if (k < p1[2]) {
    shezhi(canvas, 1);
   } else {
    shezhi(canvas, 2);
   }
  }
 
  //動(dòng)畫方法，Android的動(dòng)畫有三種，View動(dòng)畫，幀動(dòng)畫，屬性動(dòng)畫，
  //這里對(duì)動(dòng)畫方法進(jìn)行簡(jiǎn)單的封裝，只需要明白，如果存在多個(gè)顏色的話，在繪制第二個(gè)以后顏色時(shí)，每次都要先繪制先前所有顏色，再繪制當(dāng)前顏色，即可理解，這也就是動(dòng)畫的基本邏輯。
  private void shezhi(Canvas canvas, int n) {
   for (int i = 0; i <= n; i++) {
    paint.setColor(p2[i]);
    canvas.drawArc(rectF, p1[i], k - p1[i], true, paint);
   }
  }
 }
}