Canvas 绘制文本时,使用FontMetrics对象,计算位置的坐标。
1 public static class FontMetrics { 2 /** 3 * The maximum distance above the baseline for the tallest glyph in 4 * the font at a given text size. 5 */ 6 public float top; 7 /** 8 * The recommended distance above the baseline for singled spaced text. 9 */ 10 public float ascent; 11 /** 12 * The recommended distance below the baseline for singled spaced text. 13 */ 14 public float descent; 15 /** 16 * The maximum distance below the baseline for the lowest glyph in 17 * the font at a given text size. 18 */ 19 public float bottom; 20 /** 21 * The recommended additional space to add between lines of text. 22 */ 23 public float leading; 24 }
它的各基准线可以参考下图:
1 /** 绘制FontMetrics对象的各种线 */ 2 mPaint.reset(); 3 mPaint.setColor(Color.WHITE); 4 mPaint.setTextSize(80); 5 // FontMetrics对象 6 FontMetrics fontMetrics = mPaint.getFontMetrics(); 7 String text = "abcdefg"; 8 // 计算每一个坐标 9 float textWidth = mPaint.measureText(text); 10 float baseX = 30; 11 float baseY = 700; 12 float topY = baseY + fontMetrics.top; 13 float ascentY = baseY + fontMetrics.ascent; 14 float descentY = baseY + fontMetrics.descent; 15 float bottomY = baseY + fontMetrics.bottom; 16 // 绘制文本 17 canvas.drawText(text, baseX, baseY, mPaint); 18 // BaseLine描画 19 mPaint.setColor(Color.RED); 20 canvas.drawLine(baseX, baseY, baseX + textWidth, baseY, mPaint); 21 mPaint.setTextSize(20); 22 canvas.drawText("base", baseX + textWidth, baseY, mPaint); 23 // Base描画 24 canvas.drawCircle(baseX, baseY, 5, mPaint); 25 // TopLine描画 26 mPaint.setColor(Color.LTGRAY); 27 canvas.drawLine(baseX, topY, baseX + textWidth, topY, mPaint); 28 canvas.drawText("top", baseX + textWidth, topY, mPaint); 29 // AscentLine描画 30 mPaint.setColor(Color.GREEN); 31 canvas.drawLine(baseX, ascentY, baseX + textWidth, ascentY, mPaint); 32 canvas.drawText("ascent", baseX + textWidth, ascentY + 10, mPaint); 33 // DescentLine描画 34 mPaint.setColor(Color.YELLOW); 35 canvas.drawLine(baseX, descentY, baseX + textWidth, descentY, mPaint); 36 canvas.drawText("descent", baseX + textWidth, descentY, mPaint); 37 // ButtomLine描画 38 mPaint.setColor(Color.MAGENTA); 39 canvas.drawLine(baseX, bottomY, baseX + textWidth, bottomY, mPaint); 40 canvas.drawText("buttom", baseX + textWidth, bottomY + 10, mPaint);
相信通过以上程序,能够很好的理解topLine,buttomLine,baseLine,ascentLine,descentLine。
另外:Paint类有两个方法
1 /** 2 * Return the distance above (negative) the baseline (ascent) based on the 3 * current typeface and text size. 4 * 5 * @return the distance above (negative) the baseline (ascent) based on the 6 * current typeface and text size. 7 */ 8 public native float ascent(); 9 10 /** 11 * Return the distance below (positive) the baseline (descent) based on the 12 * current typeface and text size. 13 * 14 * @return the distance below (positive) the baseline (descent) based on 15 * the current typeface and text size. 16 */ 17 public native float descent();
ascent():the distance above the baseline(baseline以上的height)
descent():the distance below the baseline(baseline以下的height)
所以ascent() + descent() 可以看成文字的height。
到此为止,怎么获取文字的height和width都已经揭晓了:
获取height : mPaint.ascent() + mPaint.descent()
获取width : mPaint.measureText(text)
时间: 2024-10-01 00:28:58