在 android 中绘制彩虹色环

Question

我一直在尝试使用以下代码在 android 中绘制彩虹色环：

public void init(){
    ringPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    ringPaint.setStyle(Paint.Style.STROKE);
    ringPaint.setStrokeWidth(8f);
    ringPaint.setShader(new SweepGradient(0, 0, COLORS2, null));
}



@Override
protected void onDraw(Canvas canvas) {
    canvas.drawCircle(getWidth()/2f,getHeight()/2f ,getHeight()/2f - 16f,ringPaint);
}

COLOR2 的值如下：

final int[] COLORS2 = new int[]{Color.parseColor("#33004c"), Color.parseColor("#4600d2"),
                                Color.parseColor("#0000ff"), Color.parseColor("#0099ff"),
                                Color.parseColor("#00eeff"),Color.parseColor("#00FF7F"),
                                Color.parseColor("#48FF00"),Color.parseColor("#B6FF00"),
                                Color.parseColor("#FFD700"),Color.parseColor("#ff9500"),
                                Color.parseColor("#FF6200"),Color.parseColor("#FF0000"),
                                Color.parseColor("#33004c")};

问题是我只得到颜色的一个子集，数组中可能有 3 或 4 种不同的颜色，我不完全确定为什么，任何人都可以就为什么会这样提供一些建议案例？

Answer 1

创建 SweepGradient 时应指定视图中心而不是 0,0

请看例子

public class CustomView extends View {

    private Paint ringPaint;

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

    public void init() {
        ringPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        ringPaint.setStyle(Paint.Style.STROKE);
        ringPaint.setStrokeWidth(8f);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        ringPaint.setShader(new SweepGradient(getWidth() / 2, getHeight() / 2, COLORS2, null));
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawCircle(getWidth() / 2f, getHeight() / 2f, getHeight() / 2f - 16f, ringPaint);
    }
}

在 android 中绘制彩虹色环

Drawing a rainbow colored ring in android

android

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ondraw

sweepgradient