截取字符串，改变第N个字符的颜色；自定义方法，oncreat中调用

用到过很多次，每次在用的时候，思路就会断线，以此特意写出来，帮助自己记忆；

修改TextView 中部分文字的颜色

textView = (TextView) findViewById(R.id.textview);
SpannableStringBuilder builder = new SpannableStringBuilder(textView.getText().toString());

//ForegroundColorSpan 为文字前景色，BackgroundColorSpan为文字背景色
ForegroundColorSpan redSpan = new ForegroundColorSpan(Color.RED);
ForegroundColorSpan whiteSpan = new ForegroundColorSpan(Color.WHITE);
ForegroundColorSpan blueSpan = new ForegroundColorSpan(Color.BLUE);
ForegroundColorSpan greenSpan = new ForegroundColorSpan(Color.GREEN);
ForegroundColorSpan yellowSpan = new ForegroundColorSpan(Color.YELLOW);



builder.setSpan(redSpan, 0, 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
builder.setSpan(whiteSpan, 1, 2, Spannable.SPAN_INCLUSIVE_INCLUSIVE);
builder.setSpan(blueSpan, 2, 3, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
builder.setSpan(greenSpan, 3, 4, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
builder.setSpan(yellowSpan, 4,5, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
textView.setText(builder);

二、外部方法调用

private TextView tv_samplenumber_lan;

tv_samplenumber_lan=(TextView) findViewById(R.id.tv_samplenumber_lan);

tv_samplenumber_lan=dofor(tv_samplenumber_lan);

public static TextView dofor(TextView str){
    SpannableStringBuilder builder = new SpannableStringBuilder(str.getText().toString());
  //ForegroundColorSpan 为文字前景色，BackgroundColorSpan为文字背景色
    ForegroundColorSpan redSpan = new ForegroundColorSpan(Color.RED);
    if (str.getText().toString().substring(4,5).equals("*")){
    builder.setSpan(redSpan, 4,5, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
    }else if (str.getText().toString().substring(7,8).equals("*")){
     builder.setSpan(redSpan, 7,8, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
    }
    str.setText(builder);
    return str;
}

特意附上大神给讲解的实例代码