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}; //存放弧度的数组 //定义存放颜色的数组 private int[] p2 = {Color.GREEN, Color.YELLOW, Color.RED}; Paint paint = new Paint(); //画笔 private float k; //弧度变动后的值 //定义矩形，用户确定描绘的饼状图位置 private final RectF rectF = new RectF(100, 100, 800, 800); //定义 public PointView(Context context) { super(context); paint.setStyle(Paint.Style.FILL); //设置画笔为填充 paint.setStrokeWidth(10f); //设置画笔宽度 paint.setAntiAlias(true); //抗锯齿 //属性动画 ValueAnimator animator = ValueAnimator.ofFloat(0, 360); animator.setDuration(1000); //设置动画时间 animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { k = (float) animation.getAnimatedValue(); //获取变动后的值 invalidate(); //刷新布局 } }); animator.start(); //启动动画 } @SuppressLint("DrawAllocation") @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP) @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); //这里做了不同颜色的范围判断，还可以进行封装，为了便于学习，就没有再次封装 if (k < p1[1]) { shezhi(canvas, 0); } else if (k < p1[2]) { shezhi(canvas, 1); } else { shezhi(canvas, 2); } } //动画方法，Android的动画有三种，View动画，帧动画，属性动画， //这里对动画方法进行简单的封装，只需要明白，如果存在多个颜色的话，在绘制第二个以后颜色时，每次都要先绘制先前所有颜色，再绘制当前颜色，即可理解，这也就是动画的基本逻辑。 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); } } }} 
