android 渐变 环转圈

如图

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.SweepGradient;
import android.util.AttributeSet;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.widget.LinearLayoutCompat;

public class CircleAnimationView extends LinearLayoutCompat {
    //色值
    private int[] mColors = {Color.parseColor("#aaE7FC"),
            Color.parseColor("#008DCB"),
            Color.parseColor("#aaE7FC")};
    //环的宽度
    private int mRingW = 30;
    private Paint mPaint;
    //画布旋转的角度
    private int angle = 0;
    private SweepGradient sweepGradient;
    private final Runnable runnable = this::invalidate;

    public CircleAnimationView(@NonNull Context context) {
        super(context);
        init();
    }

    public CircleAnimationView(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public CircleAnimationView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(mRingW);
    }

    @Override
    protected void dispatchDraw(Canvas canvas) {
        super.dispatchDraw(canvas);
        final int viewWidth = getWidth();
        canvas.save();
        int px = (viewWidth - mRingW * 2) >> 1;
        canvas.rotate(angle, px, px);
        drawCircle(canvas, viewWidth);
        canvas.restore();
    }

    private void drawCircle(Canvas canvas, int viewWidth) {
        int center = viewWidth >> 1;
        if (sweepGradient == null) {
            sweepGradient = new SweepGradient(center,
                    center,
                    mColors, null);
            mPaint.setShader(sweepGradient);
        }
        canvas.drawCircle(center - mRingW, center - mRingW, center-mRingW*2, mPaint);
        angle++;
        post(runnable);
    }
}