使用 android 中的 canvas 旋转创建具有 4 段的圆

Question

我需要像这样用四种随机颜色创建一个分段圆：

http://vectips.com/wp-content/uploads/2015/04/39.png。 “4 段围成一圈”

我参考 android 关于使用 canvas.drawArc() 的文档编写了以下代码，但它没有按照我的预期工作，因为它只显示一个片段。

           Bitmap bitMap = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);

    bitMap = bitMap.copy(bitMap.getConfig(), true);
    // Construct a canvas with the specified bitmap to draw into
    Canvas canvas = new Canvas(bitMap);
    // Create a new paint with default settings.
    Paint paint = new Paint();
    // smooths out the edges of what is being drawn
    paint.setAntiAlias(true);
    // set color
    paint.setColor(Color.BLUE);

    paint.setStrokeWidth(4.5f);


    RectF oval = new RectF(200F, 200F, 450F, 450F);

    paint.setStyle(Paint.Style.FILL);
    canvas.drawArc(oval, 0F, 90F, true, paint);
    paint.setColor(Color.GREEN);
    canvas.drawArc(oval, 90F, 90F, true, paint);
    paint.setColor(Color.RED);

    canvas.drawArc(oval, 180F, 90F, true, paint);
    paint.setColor(Color.BLACK);

    canvas.drawArc(oval, 270F, 90F, true, paint);

    imageView.setImageBitmap(bitMap);

Answer 1

你的圆弧角度不对。看drawArc Canvas reference，角度参数是这样的：

startAngle - 圆弧开始的起始角度（以度为单位）
sweepAngle - 顺时针测量的扫描角度（以度为单位）

你的最后一条弧线覆盖了之前的所有弧线。你应该做类似的事情（下面的 Kotlin 代码）：

private val oval = RectF(200F, 200F, 450F, 450F)

private val paint = Paint()

override fun onDraw(canvas: Canvas) {
  paint.style = Paint.Style.FILL

  paint.color = Color.BLACK
  canvas.drawArc(oval, 0F, 90F, true, paint)
  paint.color = Color.BLUE
  canvas.drawArc(oval, 90F, 90F, true, paint)
  paint.color = Color.RED
  canvas.drawArc(oval, 180F, 90F, true, paint)
  paint.color = Color.GREEN
  canvas.drawArc(oval, 270F, 90F, true, paint)
}

会画出类似的东西：

Java版本：

  private RectF oval = new RectF(0F,0F,100F,100F);

  private Paint paint = new Paint();

  @Override
  protected void onDraw(Canvas canvas) {
    paint.setStyle(Paint.Style.FILL);

    paint.setColor(Color.BLACK);
    canvas.drawArc(oval, 0F, 90F, true, paint);
    paint.setColor(Color.BLUE);
    canvas.drawArc(oval, 90F, 1800F, true, paint)
    paint.setColor(Color.RED);
    canvas.drawArc(oval, 0F, 190F, true, paint)
    paint.setColor(Color.GREEN);
    canvas.drawArc(oval, 270F, 360F, true, paint)
  }

使用 android 中的 canvas 旋转创建具有 4 段的圆

Creating a circle with 4 segments using canvas in android with rotation

android

android-canvas

android-graphics