[2545]字体加粗的几种方法

平方X 发表于 2018-7-3 16:55:56

# 0x00 总结
各方法最终都作用于字体或 Paint
除对 Paint 直接操作外，textStyle，setTypeface，StyleSpan，b 标签这几种方法
最后都会使用字体，判断字体如果没有加粗，再设置 Paint#setFakeBoldText

# 0x01 textStyle 和 android.widget.TextView#setTypeface
TextView_textStyle 是 TextView 的属性，作用于字体

android.widget.TextView#setTypefaceFromAttrs
android.widget.TextView#setTypeface(android.graphics.Typeface, int)

public void setTypeface(Typeface tf, int style) {
   if (style > 0) {
         if (tf == null) {
            tf = Typeface.defaultFromStyle(style);
         } else {
            tf = Typeface.create(tf, style);
         }

         setTypeface(tf);
         // now compute what (if any) algorithmic styling is needed
         int typefaceStyle = tf != null ? tf.getStyle() : 0;
         int need = style & ~typefaceStyle;
         mTextPaint.setFakeBoldText((need & Typeface.BOLD) != 0);
         mTextPaint.setTextSkewX((need & Typeface.ITALIC) != 0 ? -0.25f : 0);
   } else {
         mTextPaint.setFakeBoldText(false);
         mTextPaint.setTextSkewX(0);
         setTypeface(tf);
   }
}
# 0x02 android.graphics.Paint#setFakeBoldText

public void setFakeBoldText(boolean fakeBoldText) {
   nSetFakeBoldText(mNativePaint, fakeBoldText);
}

上述两个方法，虽然 setTypeface 也有 setFakeBoldText
但是由于已经获取了 bold 字体，没有再对 Paint 进行操任

int need = style & ~typefaceStyle;
位非，再位与\n
如果已经 1，位非为0，位与 1 得 0\n
如果还是 0，位非为1，位与 1 得 1\n

# 0x03 使用 b 标签
`<b>`
## 最终还是设置的 StyleSpan
android.widget.TextView#TextView(android.content.Context, android.util.AttributeSet, int, int)
android.content.res.TypedArray#getText
android.content.res.TypedArray#loadStringValueAt
android.content.res.StringBlock#get
public CharSequence get(int idx) {
   synchronized (this) {
         ...
         String str = nativeGetString(mNative, idx);
         CharSequence res = str;
         int[] style = nativeGetStyle(mNative, idx);
               ...
               if (styleTag.equals("b")) {
                     mStyleIDs.boldId = styleId;
               }
               ...
            res = applyStyles(str, style, mStyleIDs);
         }
         if (mStrings != null) mStrings = res;
         else mSparseStrings.put(idx, res);
         return res;
   }
}
android.content.res.StringBlock#applyStyles
   if (type == ids.boldId) {
         buffer.setSpan(new StyleSpan(Typeface.BOLD),
                        style, style+1,
                        Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
   }
## android.text.style.StyleSpan#apply
private static void apply(Paint paint, int style) {
   int oldStyle;

   Typeface old = paint.getTypeface();
   if (old == null) {
         oldStyle = 0;
   } else {
         oldStyle = old.getStyle();
   }

   int want = oldStyle | style;

   Typeface tf;
   if (old == null) {
         tf = Typeface.defaultFromStyle(want);
   } else {
         tf = Typeface.create(old, want);
   }

   int fake = want & ~tf.getStyle();

   if ((fake & Typeface.BOLD) != 0) {
         paint.setFakeBoldText(true);
   }

   if ((fake & Typeface.ITALIC) != 0) {
         paint.setTextSkewX(-0.25f);
   }

   paint.setTypeface(tf);
}

页: [1]

平方X's Archiver

[2545]字体加粗的几种方法