Android canvas drawText y 文本的位置
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Android canvas drawText y-position of text
提问by darksaga
I'm using a Canvas to create a Drawable with some background and some text. The drawable is used as a compound drawable inside an EditText.
我正在使用 Canvas 创建一个带有一些背景和一些文本的 Drawable。可绘制对象用作 EditText 内的复合可绘制对象。
The text is drawn via drawText() on the canvas, but I do have an issue with the y-position of the drawn text in some cases. In those cases parts of some characters are cut off (see image links).
文本是通过画布上的 drawText() 绘制的，但在某些情况下，绘制文本的 y 位置确实存在问题。在这种情况下，某些字符的一部分会被截断（参见图片链接）。
Characters without positioning issue:
没有定位问题的字符：
http://i50.tinypic.com/zkpu1l.jpg
http://i50.tinypic.com/zkpu1l.jpg
Characters with positioning issue, text contains 'g', 'j', 'q', etc.:
有定位问题的字符，文本包含“g”、“j”、“q”等：
http://i45.tinypic.com/vrqxja.jpg
http://i45.tinypic.com/vrqxja.jpg
You can find a code snippet to reproduce the issue below.
您可以在下面找到一个代码片段来重现该问题。
Does any expert know how to determine the proper offset for the y position?
有没有专家知道如何确定 y 位置的正确偏移量？
public void writeTestBitmap(String text, String fileName) {
// font size
float fontSize = new EditText(this.getContext()).getTextSize();
fontSize+=fontSize*0.2f;
// paint to write text with
Paint paint = new Paint();
paint.setStyle(Style.FILL);
paint.setColor(Color.DKGRAY);
paint.setAntiAlias(true);
paint.setTypeface(Typeface.SERIF);
paint.setTextSize((int)fontSize);
// min. rect of text
Rect textBounds = new Rect();
paint.getTextBounds(text, 0, text.length(), textBounds);
// create bitmap for text
Bitmap bm = Bitmap.createBitmap(textBounds.width(), textBounds.height(), Bitmap.Config.ARGB_8888);
// canvas
Canvas canvas = new Canvas(bm);
canvas.drawARGB(255, 0, 255, 0);// for visualization
// y = ?
canvas.drawText(text, 0, textBounds.height(), paint);
try {
FileOutputStream out = new FileOutputStream(fileName);
bm.compress(Bitmap.CompressFormat.JPEG, 100, out);
} catch (Exception e) {
e.printStackTrace();
}
}
采纳答案by Tim
I think it's probably a mistake to assume that textBounds.bottom = 0. For those descending characters, the bottom parts of those characters are probably below 0 (which means textBounds.bottom > 0). You probably want something like:
我认为假设 textBounds.bottom = 0 可能是错误的。对于那些降序字符，这些字符的底部可能低于 0（这意味着 textBounds.bottom > 0）。你可能想要这样的东西：
canvas.drawText(text, 0, textBounds.top, paint); //instead of textBounds.height()
canvas.drawText(text, 0, textBounds.top, paint); //instead of textBounds.height()
If your textBounds is from +5 to -5, and you draw text at y=height (10), then you'll only see the top half of the text.
如果您的 textBounds 是从 +5 到 -5，并且您在 y=height (10) 处绘制文本，那么您将只能看到文本的上半部分。
回答by damix911
I believe that if you want to draw text near the upper left corner you should do this:
我相信如果你想在左上角附近绘制文本，你应该这样做：
canvas.drawText(text, -textBounds.left, -textBounds.top, paint);
And you can move around the text by summing the desired amount of displacement to the two coordinates:
您可以通过将所需的位移量与两个坐标相加来移动文本：
canvas.drawText(text, -textBounds.left + yourX, -textBounds.top + yourY, paint);
The reason why this works (at least for me) is that getTextBounds() tells you where drawText() would draw the text in the event that x=0 and y=0. So you have to counteract this behavior by subtracting the displacement (textBounds.left and textBounds.top) introduced by the way text is handled in Android.
这样做的原因（至少对我而言）是 getTextBounds() 告诉您在 x=0 和 y=0 的情况下 drawText() 将在何处绘制文本。因此，您必须通过减去 Android 中处理文本的方式引入的位移（textBounds.left 和 textBounds.top）来抵消这种行为。
In this answerI elaborate a little more on this topic.
在这个答案中，我详细阐述了这个主题。
