//leveraging the extension functions
fun TextView.makeBold(){
    this.setTypeface(this.typeface,Typeface.BOLD)
}


yourTextView.makeBold()

textView.setTypeface(null, Typeface.BOLD_ITALIC);
textView.setTypeface(null, Typeface.BOLD);
textView.setTypeface(null, Typeface.ITALIC);
textView.setTypeface(null, Typeface.NORMAL);

保持以前的字体

textView.setTypeface(textView.getTypeface(), Typeface.BOLD_ITALIC)

使用textView。setTypeface(字体tf, int风格);设置TextView的样式属性。有关更多信息，请参阅开发人员文档。

正如这里所解释的，如果你需要在你的样式文本资源中使用参数，你必须转义开括号

<resources>
<string name="welcome_messages">Hello, %1$s! You have &lt;b>%2$d new messages&lt;/b>.</string>
</resources>

然后调用formatHtml(string)

Resources res = getResources();
String text = String.format(res.getString(R.string.welcome_messages), username, mailCount);
CharSequence styledText = Html.fromHtml(text);

TextView text = (TextView)findViewById(R.id.THE_TEXTVIEW_ID);

现在设置textview属性..

text.setTypeface(null, Typeface.BOLD);  //-- for only bold the text
text.setTypeface(null, Typeface.BOLD_ITALIC);  //-- for  bold & italic the text
text.setTypeface(null, Typeface.ITALIC);  // -- for  italic the text

试试这个:

TextView textview = (TextView)findViewById(R.id.textview_idname);
textview.setTypeface(null,Typeface.BOLD);