问题：寻找一个drawArc()方法与内外的半径

Question

我已经下定义的看法：

这个我已经实现了通过使用画布 drawArc() 法。然而，与这个 drawArc() 方法我不能限制弧内的半径。

什么我有的是事情是这样的：

那里只有一个外部环离开。

我需要的是一个 drawArc() 功能，我可以设置的半径内的弧形。任何人一个想法是如何做到这一点吗？

(顺便说一句，overpainting区域内不工作，因为它需要透明。画一个圈内有 Color.TRANSPARENT 画后的红色和蓝色圆锥不删除旧的色彩。它只是提出另一层上，这是透明的，并通过它，我仍然可以看到红色和蓝色)

Answer 1

您可以使用称为“透明”的Porterduff Xfermode在内部区域进行绘画。这将删除像素。

Answer 2

你可以这样做：

    Paint paint = new Paint();
    final RectF rect = new RectF();
    //Example values
    rect.set(mWidth/2- mRadius, mHeight/2 - mRadius, mWidth/2 + mRadius, mHeight/2 + mRadius); 
    paint.setColor(Color.GREEN);
    paint.setStrokeWidth(20);
    paint.setAntiAlias(true);
    paint.setStrokeCap(Paint.Cap.ROUND);
    paint.setStyle(Paint.Style.STROKE);
    canvas.drawArc(rect, -90, 360, false, paint);

关键是在 paint.setStyle(Paint.Style.STROKE);, 它作物的弧中心的行程，你一定义在setStrokeWidth(例中汲取的一个弧形半径为mRadius和20像素厚)。

希望它能帮助!

Answer 3

private static final float CIRCLE_LIMIT = 359.9999f;
/**
 * Draws a thick arc between the defined angles, see {@link Canvas#drawArc} for more.
 * This method is equivalent to
 * <pre><code>
 * float rMid = (rInn + rOut) / 2;
 * paint.setStyle(Style.STROKE); // there's nothing to fill
 * paint.setStrokeWidth(rOut - rInn); // thickness
 * canvas.drawArc(new RectF(cx - rMid, cy - rMid, cx + rMid, cy + rMid), startAngle, sweepAngle, false, paint);
 * </code></pre>
 * but supports different fill and stroke paints.
 * 
 * @param canvas
 * @param cx horizontal middle point of the oval
 * @param cy vertical middle point of the oval
 * @param rInn inner radius of the arc segment
 * @param rOut outer radius of the arc segment
 * @param startAngle see {@link Canvas#drawArc}
 * @param sweepAngle see {@link Canvas#drawArc}, capped at &plusmn;360
 * @param fill filling paint, can be <code>null</code>
 * @param stroke stroke paint, can be <code>null</code>
 * @see Canvas#drawArc
 */
public static void drawArcSegment(Canvas canvas, float cx, float cy, float rInn, float rOut, float startAngle,
        float sweepAngle, Paint fill, Paint stroke) {
    if (sweepAngle > CIRCLE_LIMIT) {
        sweepAngle = CIRCLE_LIMIT;
    }
    if (sweepAngle < -CIRCLE_LIMIT) {
        sweepAngle = -CIRCLE_LIMIT;
    }

    RectF outerRect = new RectF(cx - rOut, cy - rOut, cx + rOut, cy + rOut);
    RectF innerRect = new RectF(cx - rInn, cy - rInn, cx + rInn, cy + rInn);

    Path segmentPath = new Path();
    double start = toRadians(startAngle);
    segmentPath.moveTo((float)(cx + rInn * cos(start)), (float)(cy + rInn * sin(start)));
    segmentPath.lineTo((float)(cx + rOut * cos(start)), (float)(cy + rOut * sin(start)));
    segmentPath.arcTo(outerRect, startAngle, sweepAngle);
    double end = toRadians(startAngle + sweepAngle);
    segmentPath.lineTo((float)(cx + rInn * cos(end)), (float)(cy + rInn * sin(end)));
    segmentPath.arcTo(innerRect, startAngle + sweepAngle, -sweepAngle);
    if (fill != null) {
        canvas.drawPath(segmentPath, fill);
    }
    if (stroke != null) {
        canvas.drawPath(segmentPath, stroke);
    }
}

可以通过复制来扩展到椭圆形弧 rInn 和 rOut 对于X和Y方向。

也不是问题的一部分，而是要在细分市场中间绘制文本：

textPaint.setTextAlign(Align.CENTER);
Path midway = new Path();
float r = (rIn + rOut) / 2;
RectF segment = new RectF(cx - r, cy - r, cx + r, cy + r);
midway.addArc(segment, startAngle, sweepAngle);
canvas.drawTextOnPath("label", midway, 0, 0, textPaint);

Answer 4

您可以尝试遵循ShapapaWabable

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
<item>
    <shape android:shape="oval" >
        <size
            android:height="56dp"
            android:width="56dp" />

        <stroke
            android:width="10dp"
            android:color="#0000ff" />
    </shape>
</item>
<item>
    <shape android:shape="oval" >
        <size
            android:height="24dp"
            android:width="25dp" />

        <stroke
            android:dashGap="10dp"
            android:dashWidth="10dp"
            android:width="10dp"
            android:color="#FF0000" />
    </shape>
</item>

Answer 5

绘制圆圈和弧。以下代码很少脏，但可能会有所帮助

        int sweepAngle sweepAngle = (360/7)%360;
    int startAngle = -90;
    int x = getWidth()/2;
    int y = getHeight()/2;
    int radius;
    radius = getWidth()/2-50;
    paint.setStyle(Paint.Style.STROKE);
    paint.setStrokeWidth(50);
    paint.setColor(Color.WHITE);

    paint.setColor(Color.parseColor("#CD5C5C"));
    mBarPaintFill.setAntiAlias(true);

    canvas.drawCircle(x , y , radius, paint);
    paint.setColor(Color.BLUE);
    for (int i = 1 ; i<=5 ; i++){

        canvas.drawArc(x-radius,y-radius,x+radius,y+radius,startAngle,sweepAngle,false,paint);
        startAngle = (startAngle + sweepAngle+20)%360;
    }