最近在自定義View中繪制文字的時候遇到需要測量文字的情況，查了一些資料，寫下以備用。
API介紹
字體有6個參數(shù)：
- baseline
- ascent
- bottom
- descent
- leading
- top
baseline
基線的定義
The invisible line where all characters sit.
Definition: In typography, the baseline is the imaginary line upon which a line of text rests. In most typefaces, the descenders on characters such as g or p extend down below the baseline while curved letters such as c or o extend ever-so-slightly below the baseline. The baseline is the point from which other elements of type are measured including x-height and leading. The baseline is also significant in the alignment of drop caps and other page elements.
In typography and penmanship, the baseline is the line upon which most letters “sit” and below which descenders extend.
In the example to the right, the letter ‘p’ has a descender; the other letters sit on the (red) baseline.
Most, though not all, typefaces are similar in the following ways as regards the baseline:
- capital letters sit on the baseline. The most common exceptions are the J and Q.
- Lining figures (see Arabic numerals) sit on the baseline.
- The following text figures have descenders: 3 4 5 7 9.
- The following lowercase letters have descenders: g j p q y.
- Glyphs with rounded lower extents (0 3 5 6 8 c C G J o O Q U) dip very slightly below the baseline (“overshoot”) to create the optical illusion that they sit on the baseline. Peter Karow’s Digital Typefaces suggests that typical overshoot is about 1.5%.
The vertical distance of the base lines of consecutive lines in a paragraph is also known as line height or leading, although the latter can also refer to the baseline distance minus the font size.
基線是一條想象的線包裹著一個字符的上下兩端，但不包裹字符的“下擺”。
ascent
baseline到字體頂部的距離。
bottom
一個或多個字符中的最低的字符到baseline的距離，也可以視作所有字符的descent值的最大值。
descent
字符自baseline以下到最低處的距離。
leading
行距，可以理解為當(dāng)前行的所有字符的最低處到下一行字符的頂部的距離。
top
一個或多個字符中的最高處字符到baseline的距離，也可以視作所有字符的ascent的最大值。
獲取文字高度
方法一：
// 此方法沒有計算leading
Paint paint = new Paint();
// 設(shè)置字體大小
paint.setTextSize(xxx);
int height = paint.descent() - paint.ascent();
方法二：
Paint paint = new Paint();
// 設(shè)置字體大小
paint.setTextSize(xxx);
// 設(shè)置字體
paint.setTypeface(Typeface.xxx);
Paint.FontMetrics fontMetrics = paint.getFontMetrics();
float height1 = fontMetrics.descent - fontMetrics.ascent + fontMetrics.leading;
// height2測得的高度可能稍微比height1高一些
float height2 = fontMetrics.bottom - fontMetrics.top + fontMetrics.leading;
測量文字寬度
Paint paint = new Paint();
String str = "xxx";
// 設(shè)置字體大小
paint.setTextSize(xxx);
// 文字的寬度
float strWidth = paint.measureText(str);
通過文字所在的矩形區(qū)域獲得寬和高（不如measureText方法得到的值精確）
Paint paint = new Paint();
String str = "xxx";
Rect rect = new Rect();
// 參數(shù)1：需要測量的字符串
// 參數(shù)2：需要測量的字符串的第一個字符的索引
// 參數(shù)3：需要測量的字符串的最后一個字符的索引+1，通常是需要測量的字符串的長度
// 參數(shù)4：Rect對象
paint.getTextBounds(str, 0, str.length(), rect);
// 文字的寬度
int width = rect.width();
// 文字的高度
int height = rect.height();
