如何在onDraw方法之外获取自定义视图的画布大小？

Question

我需要能够访问视图画布的大小来执行一些计算.由于某种原因,传递给的视图onSizeChanged的大小不同于传递给的画布的大小onDraw.我当前的解决方法使用布尔标志来确定何时需要进行计算.

理想的解决方案将允许我在onSizeChanged方法中进行这些计算,所以我想知道......有什么办法可以Canvas在onDraw方法之外得到对象(或者至少它的维度)吗？

我的代码如下.它以给定角度绘制圆的半径.当我canvas.centerX()用来确定半径的起点和终点时,一切都很完美.如果我使用传入的参数onSizeChanged,它甚至远程接近正确.

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  super.onSizeChanged(w, h, oldw, oldh);
  mSizeChanged = true;
}

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

  if (mSizeChanged) {
    RectF bounds = new RectF(canvas.getClipBounds());
    float centerX = bounds.centerX();
    float centerY = bounds.centerY();
    float radianAngle = (float) Math.toRadians(mStartAngle);

    mRadius[0] = center;
    mRadius[1] = center;
    mRadius[2] = center + center * FloatMath.cos(radianAngle);
    mRadius[3] = center + center * FloatMath.sin(radianAngle);
    mSizeChanged = false;
  }

  mPaint.setColor(0xFF330000);
  mPaint.setStrokeWidth(1);
  canvas.drawLines(mRadius, mPaint);
}

Answer 1

出于绘图目的,您不应该真正使用Canvas对象的尺寸.

只需使用onSizeChanged方法中提供给您的尺寸即可.您可以存储要在onDraw方法中使用的尺寸,也可以调整大小/绘制到可以在以后绘制的支持位图.

更新:

快速掀起一些代码,它看起来像这样:

public class CustomView extends View{
    private Paint paint;
    private int w;
    private int h;

    public CustomView(Context context, AttributeSet attr) {
        super(context, attr);
        paint = new Paint();
        paint.setTextAlign(Align.CENTER);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        this.w = w;
        this.h = h;
        super.onSizeChanged(w, h, oldw, oldh);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawColor(Color.WHITE);
        canvas.drawText("TEST", w/2, h/2, paint);   
    }
}

更新2

循环代码更新后.

我们做得到:

   @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawColor(Color.WHITE);
        float centerX = (float) w/2;
        float centerY = (float) h/2;
        float radianAngle = (float) Math.toRadians(startAngle);

        radius[0] = centerX;
        radius[1] = centerY;
        radius[2] = centerX + centerX * FloatMath.cos(radianAngle);
        radius[3] = centerY + centerY * FloatMath.sin(radianAngle);

        paint.setColor(0xFF330000);
        paint.setStrokeWidth(1);
        canvas.drawLines(radius, paint);
    }

您会看到这现在适用于任何大小的视图.