/**
* Class that describes the various各种 metrics指标 for a font at a given text size.
* Remember, Y values increase going down, so those values will be positive正数,
* and values that measure distances距离 going up will be negative负数. This class
* is returned by getFontMetrics().
*/
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;
//【字符顶部】The recommended推荐的 distance above the baseline for singled spaced text.
public float ascent;
//【字符底部】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;
//【字符行间距】The recommended additional额外的 space to add between lines两行之间 of text.
public float leading;
}
//Return the distance above (negative) the baseline (ascent) based on the current typeface字体 and text size.
public native float ascent();
//Return the distance below (positive) the baseline (descent) based on the current typeface and text size.
public native float descent();
/**
* Return the width of the text.
*
* @param text The text to measure. Cannot be null.
* @param start The index of the first character to start measuring
* @param end 1 beyond the index of the last character to measure
* @return The width of the text
*/
public float measureText(String text, int start, int end) {
if (text == null) throw new IllegalArgumentException("text cannot be null");
if ((start | end | (end - start) | (text.length() - end)) < 0) throw new IndexOutOfBoundsException();
if (text.length() == 0 || start == end) return 0f;
if (!mHasCompatScaling) return (float) Math.ceil(native_measureText(text, start, end, mBidiFlags));
final float oldSize = getTextSize();
setTextSize(oldSize*mCompatScaling);
float w = native_measureText(text, start, end, mBidiFlags);
setTextSize(oldSize);
return (float) Math.ceil(w*mInvCompatScaling);
}
/**
* Return in bounds (allocated by the caller 由调用者分配) the smallest最小的 rectangle that
* encloses围起来 all of the characters, with an implied origin默认的起始位置 at (0,0).
* @param text String to measure and return its bounds
* @param start Index of the first char in the string to measure
* @param end 1 past the last char in the string measure
* @param bounds Returns the unioned bounds of all the text. Must be allocated by the caller.
*/
public void getTextBounds(String text, int start, int end, Rect bounds) {
if ((start | end | (end - start) | (text.length() - end)) < 0) throw new IndexOutOfBoundsException();
if (bounds == null) throw new NullPointerException("need bounds Rect");
nativeGetStringBounds(mNativePaint, mNativeTypeface, text, start, end, mBidiFlags, bounds);
}
/**
* @return the base paint used for the text. Please use this only to
* consult查阅 the Paint‘s properties属性 and not to change them.
*/
public TextPaint getPaint() {
return mTextPaint;
}
原文：http://www.cnblogs.com/baiqiantao/p/59069dfa57617252fca5a1d4b5d447ce.html