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Android使用FontMetrics對象計算位置坐標(biāo)

更新時間：2018年12月25日 08:50:20 作者：teletian

這篇文章主要為大家詳細(xì)介紹了Android使用FontMetrics對象計算位置坐標(biāo)，具有一定的參考價值，感興趣的小伙伴們可以參考一下

Canvas繪制文本時，使用FontMetrics對象，計算位置的坐標(biāo)。

public static class FontMetrics {
  /**
   * The maximum distance above the baseline for the tallest glyph in 
   * the font at a given text size.
   */
  public float  top;
  /**
   * The recommended distance above the baseline for singled spaced text.
   */
  public float  ascent;
  /**
   * The recommended distance below the baseline for singled spaced text.
   */
  public float  descent;
  /**
   * The maximum distance below the baseline for the lowest glyph in 
   * the font at a given text size.
   */
  public float  bottom;
  /**
   * The recommended additional space to add between lines of text.
   */
  public float  leading;
}

它的各基準(zhǔn)線可以參考下圖：

上圖其實是通過代碼畫出來的，具體代碼如下：

/** 繪制FontMetrics對象的各種線 */
mPaint.reset();
mPaint.setColor(Color.WHITE);
mPaint.setTextSize(80);
// FontMetrics對象
FontMetrics fontMetrics = mPaint.getFontMetrics();
String text = "abcdefg";
// 計算每一個坐標(biāo)
float textWidth = mPaint.measureText(text);
float baseX = 30;
float baseY = 700;
float topY = baseY + fontMetrics.top;
float ascentY = baseY + fontMetrics.ascent;
float descentY = baseY + fontMetrics.descent;
float bottomY = baseY + fontMetrics.bottom;
// 繪制文本
canvas.drawText(text, baseX, baseY, mPaint);
// BaseLine描畫
mPaint.setColor(Color.RED);
canvas.drawLine(baseX, baseY, baseX + textWidth, baseY, mPaint);
mPaint.setTextSize(20);
canvas.drawText("base", baseX + textWidth, baseY, mPaint);
// Base描畫
canvas.drawCircle(baseX, baseY, 5, mPaint);
// TopLine描畫
mPaint.setColor(Color.LTGRAY);
canvas.drawLine(baseX, topY, baseX + textWidth, topY, mPaint);
canvas.drawText("top", baseX + textWidth, topY, mPaint);
// AscentLine描畫
mPaint.setColor(Color.GREEN);
canvas.drawLine(baseX, ascentY, baseX + textWidth, ascentY, mPaint);
canvas.drawText("ascent", baseX + textWidth, ascentY + 10, mPaint);
// DescentLine描畫
mPaint.setColor(Color.YELLOW);
canvas.drawLine(baseX, descentY, baseX + textWidth, descentY, mPaint);
canvas.drawText("descent", baseX + textWidth, descentY, mPaint);
// ButtomLine描畫
mPaint.setColor(Color.MAGENTA);
canvas.drawLine(baseX, bottomY, baseX + textWidth, bottomY, mPaint);
canvas.drawText("buttom", baseX + textWidth, bottomY + 10, mPaint);

相信通過以上程序，能夠很好的理解topLine，buttomLine，baseLine，ascentLine，descentLine。
另外：Paint類有兩個方法

/**
 * Return the distance above (negative) the baseline (ascent) based on the
 * current typeface and text size.
 *
 * @return the distance above (negative) the baseline (ascent) based on the
 *     current typeface and text size.
 */
public native float ascent();
 
/**
 * Return the distance below (positive) the baseline (descent) based on the
 * current typeface and text size.
 *
 * @return the distance below (positive) the baseline (descent) based on
 *     the current typeface and text size.
 */
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。

到此為止，怎么獲取文字的height和width都已經(jīng)揭曉了：

獲取height ： mPaint.ascent() + mPaint.descent()

獲取width ： mPaint.measureText(text)

以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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