如何以编程方式将笔画添加到可绘制对象？

Question

我有此代码：

我的可绘制对象包装了另一个可绘制对象（圆形）。

如何以编程方式向内部笔画添加笔画？

public final class HighlightCircleDrawable extends Drawable implements Drawable.Callback {

  private final Drawable toHighlight;
  private final Paint paint = new Paint();

//...

  public HighlightCircleDrawable(Drawable toHighlight) {
    this.toHighlight = toHighlight;
    toHighlight.setCallback(this);
    paint.setStyle(Paint.Style.FILL);
    paint.setColor(Color.GRAY);
  }

  @Override
  public void draw(Canvas canvas) {
    canvas.drawOval(pulseBounds, paint);
    toHighlight.draw(canvas);
  }

Answer 1

首先，您需要制作背景，为此您应该使用整个画布。首先填充画布，然后应用填充，但关键是为backgroundPaint使用较小的边界，以便borderPaint包围highlightPaint

final Paint borderPaint = new Paint();
borderPaint.setStyle(Paint.Style.FILL);
borderPaint.setColor(borderColor);
borderPaint.setAntiAlias(true);
borderPaint.setDither(true);

...

canvas.drawOval(rect, borderPaint);
canvas.drawOval(pulseBounds, paint);