android在画布上绘图。访问onDraw外部的画布

Question

为了访问onDraw（）之外的画布，我这样做：

 private Canvas canvas;


 public MyView(Context context, Paint paint) {
     super(context);

     canvas = new Canvas();
 }

 @Override
 protected final void onDraw(Canvas canvas) {
     canvas.save();

     this.canvas = canvas;
}

然后我用它：

 private class myScaleListener extends SimpleOnScaleGestureListener {

     @Override
     public boolean onScale(ScaleGestureDetector detector) {
        canvas.setMatrix(matrix);
     }
 }

有一个更好的方法吗？

当我从canvas.setMatrix(matrix)打电话给onDraw()时，绘图正在转移。

提前致谢！！！

Answer 1

我想如果你改变一些东西，它看起来会更好：

private Canvas canvas;

public MyView(Context context, Paint paint) {
    super(context);
    canvas = null;
}

@Override
protected final void onDraw(Canvas canvas) {
    this.canvas = canvas;
    canvas.save();
}

private class myScaleListener extends SimpleOnScaleGestureListener {<br/>

  @Override
  public boolean onScale(ScaleGestureDetector detector) {
    if(canvas != null) {
       canvas.setMatrix(matrix);
    }
  }
}

看看它是否有效，我认为应该如此。