7

我一直在为文本测量和缩放画布而苦苦挣扎。

当画布未缩放时,getTextBounds 和 measureText 会提供准确的结果。但是,当画布被缩放时,这两种方法都不会提供与打印文本的实际大小相匹配的结果。

为了测试,我使用以下 onDraw 方法创建了 View 的子类:

final float scaling = 0.51f;
final int fontSize = 50;

canvas.scale(scaling, scaling);
font = Typeface.create("Arial", Typeface.NORMAL);

Paint paint = new Paint();
paint.setColor(0xff4444ff);
paint.setTypeface(font);
paint.setTextSize(fontSize);
paint.setAntiAlias(true);

int x = 10;
int y = 100;
final String text = "Lorem ipsum dolor sit amet, consectetur adipisici elit...";
canvas.drawText(text, x, y, paint);

// draw border using getTextBounds

paint.setColor(0xffff0000);
paint.setStyle(Paint.Style.STROKE);
paint.setTypeface(font);
paint.setTextSize(fontSize);
Rect bounds = new Rect();
paint.getTextBounds(text, 0, text.length(), bounds);
bounds.offset(x, y);
paint.setColor(0x80ffff00);
canvas.drawRect(bounds, paint);

// draw border using measureText

float w = paint.measureText(text);
bounds.left = x;
bounds.right = (int) Math.ceil(bounds.left + w);
bounds.top -= 10;
bounds.bottom += 10;
paint.setColor(0x8000ffff);
paint.setPathEffect(new DashPathEffect(new float[] { 10, 10 }, 0));
canvas.drawRect(bounds, paint);

对于缩放 = 0.5,我得到以下输出: 画布缩放 0.5

对于缩放 = 0.51,显示以下结果: 画布缩放 0.51

黄色实心边框标记从 getTextBounds 传递的矩形,青色虚线矩形使用从 measureText 传递的宽度呈现。

如您所见,缩放 = 0.5 的文本小于测量尺寸,缩放 = 0.51 绘制的文本远大于测量尺寸。

任何帮助表示赞赏!

4

2 回答 2

3

好的,刚刚发现如何规避这个问题。

问题是 Paint 不知道 Canvas 缩放。因此 measureText 和 getTextBounds 提供未缩放的结果。但是由于字体大小不是线性缩放的(但是,绘制的矩形会),您必须手动弥补这种影响。

所以解决方案是:

// paint the text as usual
Paint paint = new Paint();
paint.setTypeface(font);
paint.setTextSize(fontSize);
canvas.drawText(text, x, y, paint);


// measure the text using scaled font size and correct the scaled value afterwards
Paint paint = new Paint();
paint.setTypeface(font);
paint.setTextSize(fontSize * scaling);
float w = paint.measureText(text) / scaling;
于 2011-10-13T07:48:17.330 回答
0

使用Mono for Android我必须使用显示指标,如下所示:

public override System.Drawing.SizeF MeasureString(MyFont f, string text)
{
  Rect r = new Rect();

  f.DrawingFont.GetTextBounds(text, 0, text.Length, r);

  //Manual scaling using DisplayMetrics due to Android
  //issues for compatibility with older versions
  Android.Util.DisplayMetrics metrics = new Android.Util.DisplayMetrics();
  GetDisplay.GetMetrics(metrics);

  return new System.Drawing.SizeF(r.Width(), r.Height() * metrics.Density);
}

其中f.DrawingFontAndrodid.Text.TextPaint GetDisplay 是:

private Display GetDisplay()
{
  return this.GetSystemService(Android.Content.Context.WindowService).JavaCast<Android.Views.IWindowManager>().DefaultDisplay;
}

Java中的相同方法是:

private Display getDisplay() {
    return ((WindowManager) getContext().getSystemService(
            Context.WINDOW_SERVICE)).getDefaultDisplay();
}
于 2011-10-10T14:01:56.087 回答