用不同的边框颜色Android绘制圆圈

Question

public static Bitmap drawCircle(int width,int height, int borderWidth) {
    Bitmap canvasBitmap = Bitmap.createBitmap( width, height, Bitmap.Config.ARGB_8888);
    BitmapShader shader = new BitmapShader(canvasBitmap, TileMode.CLAMP,      
            TileMode.CLAMP);
    Paint paint = new Paint();
    paint.setAntiAlias(true);
    paint.setShader(shader);
    paint.setShader(null);
    paint.setStyle(Paint.Style.STROKE);
    paint.setColor(Color.WHITE);
    paint.setStrokeWidth(borderWidth);  
    Canvas canvas = new Canvas(canvasBitmap);
    float radius = width > height ? ((float) height) / 2f : ((float) width) / 2f;
    canvas.drawCircle(width / 2, height / 2, radius - borderWidth / 2, paint);
    return canvasBitmap;
}

简单的这个代码绘制一个带有白色边框的圆圈,但是我希望边框的一部分是黑色而另一部分是白色的.40%的黑色,60%的白色

如何才能做到这一点？

Answer 1

试试这个代码

class MyView extends View
{
    private Paint paint;

    public MyView(Context context, int x, int y)
    {
        super(context);
        paint = new Paint();
        // PorterDuffXfermode xfermode = new PorterDuffXfermode(PorterDuff.Mode.CLEAR);

        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.RED);


        paint.setAlpha(255);
        // paint.setXfermode(xfermode);
        paint.setAntiAlias(true);
        // setBackgroundColor(Color.BLACK);
    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        canvas.drawCircle(100, 100, 50, paint);
    }
}

Answer 2

这里有一个实用方法，用于用一种颜色填充圆圈并用另一种颜色描边圆圈边框。

使用第二种方法传入现有的 Paint 实例，例如设置抗锯齿标志或防止 onDraw() 期间的内存分配。

public static void fillCircleStrokeBorder(
        Canvas c, float cx, float cy, float radius,
        int circleColor, float borderWidth, int borderColor) {
    fillCircleStrokeBorder(c, cx, cy, radius, circleColor, borderWidth, borderColor, new Paint());
}

public static void fillCircleStrokeBorder(
        Canvas c, float cx, float cy, float radius,
        int circleColor, float borderWidth, int borderColor, Paint p) {

    int saveColor = p.getColor();
    p.setColor(circleColor);
    Paint.Style saveStyle = p.getStyle();
    p.setStyle(Paint.Style.FILL);
    c.drawCircle(cx, cy, radius, p);
    if (borderWidth > 0) {
        p.setColor(borderColor);
        p.setStyle(Paint.Style.STROKE);
        float saveStrokeWidth = p.getStrokeWidth();
        p.setStrokeWidth(borderWidth);
        c.drawCircle(cx, cy, radius - (borderWidth / 2), p);
        p.setStrokeWidth(saveStrokeWidth);
    }
    p.setColor(saveColor);
    p.setStyle(saveStyle);
}