SpannableString(Android 富文本)简介

通俗来讲，就是富文本的Android实现方式，跟iOS的NSMutableAttributedString一样的作用

使用方法

SpannableString spannableString = new SpannableString("我是一段需要被修饰的字符串");
BackgroundColorSpan backgroundColorSpan = new BackgroundColorSpan(Color.GREEN);
spannableString.setSpan(backgroundColorSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
mTextView.setText(spannableString);

setSpan这个是核心方法，有四个参数
参数1：具体要修改的样式，颜色、大小等等，上图代码就是修改颜色
参数2：修改的起始下标
参数3：修改的结束下标
参数4：就是是否包含开始坐标或者结束坐标，排列组合下面四种类型

`SPAN_INCLUSIVE_EXCLUSIVE`：包括开始下标，但不包括结束下标
`SPAN_EXCLUSIVE_INCLUSIVE`：不包括开始下标，但包括结束下标
`SPAN_INCLUSIVE_INCLUSIVE`：既包括开始下标，又包括结束下标
`SPAN_EXCLUSIVE_EXCLUSIVE`：不包括开始下标，也不包括结束下标

记录几个常用的 span(不知道是不是这么叫，反正用于setSpan)

• ForegroundColorSpan修改颜色

BackgroundColorSpan backgroundColorSpan = new BackgroundColorSpan(Color.GREEN);

• BackgroudColorSpan修改背景色

BackgroundColorSpan backgroundColorSpan = new BackgroundColorSpan(Color.GREEN);

• ClickableSpan,设置文字可点击

SpannableString spannableString = new SpannableString("我是一段需要被修饰的字符串");
ClickableSpan clickableSpan = new ClickableSpan() {
    @Override
    public void onClick(View widget) {
        Toast.makeText(MainActivity.this, "我是一段需要被修饰的字符串", Toast.LENGTH_SHORT).show();
    }
    @Override
    public void updateDrawState(TextPaint ds) {
        ds.setUnderlineText(false);
    }
};
spannableString.setSpan(clickableSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
mTextView.setMovementMethod(LinkMovementMethod.getInstance());
mTextView.setText(spannableString);

• URLSpan文字超链接

URLSpan urlSpan = new URLSpan("https://www.baidu.com/s?ie=UTF-8&wd=字符串");
spannableString.setSpan(urlSpan, 10, 13, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
mTextView.setMovementMethod(LinkMovementMethod.getInstance());
mTextView.setText(spannableString);

• RelativeSizeSpan文字相对大小,相比其他文字的倍数

RelativeSizeSpan relativeSizeSpan = new RelativeSizeSpan(1.5f);

• AbsoluteSizeSpan设置文字大小,第一个参数是大小，第二个参数true代表dp,false代表px

AbsoluteSizeSpan absoluteSizeSpan = new AbsoluteSizeSpan(40, true);

• StyleSpan设置字体样式，斜体粗体等

StyleSpan boldSpan = new StyleSpan(Typeface.BOLD);
StyleSpan italicSpan = new StyleSpan(Typeface.ITALIC);
StyleSpan boldItalicSpan = new StyleSpan(Typeface.BOLD_ITALIC);
spannableString.setSpan(boldSpan, 0, 2, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
spannableString.setSpan(italicSpan, 2, 4, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
spannableString.setSpan(boldItalicSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);

• TypefaceSpan设置文字字体类型

TypefaceSpan monospace = new TypefaceSpan("monospace");
TypefaceSpan serif = new TypefaceSpan("serif");
TypefaceSpan sans_serif = new TypefaceSpan("sans-serif");
spannableString.setSpan(monospace, 0, 2, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
spannableString.setSpan(serif, 2, 4, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
spannableString.setSpan(sans_serif, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);

• TextAppearanceSpan通过系统的style资源设置字体样式

TextAppearanceSpan textAppearanceSpan = new TextAppearanceSpan(this, android.R.style.TextAppearance_Material);
spannableString.setSpan(textAppearanceSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);

• UnderlineSpan设置文字下划线

UnderlineSpan underlineSpan = new UnderlineSpan();
spannableString.setSpan(underlineSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);

• StrikethroughSpan设置文字删除线

StrikethroughSpan strikethroughSpan = new StrikethroughSpan();
spannableString.setSpan(strikethroughSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);

• SuperscriptSpan 设置文字为上标

SuperscriptSpan superscriptSpan = new SuperscriptSpan();
RelativeSizeSpan relativeSizeSpan = new RelativeSizeSpan(0.8f);
spannableString.setSpan(relativeSizeSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
spannableString.setSpan(superscriptSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);

• SubscriptSpan设置文字为下标

SubscriptSpan subscriptSpan = new SubscriptSpan();
RelativeSizeSpan relativeSizeSpan = new RelativeSizeSpan(0.8f);
spannableString.setSpan(relativeSizeSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
spannableString.setSpan(subscriptSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);

• ImageSpan文字上拼接图片

SpannableString spannableString = new 
ImageSpan imageSpan = new ImageSpan(this, R.drawable.ic_eason);
spannableString.setSpan(imageSpan, 4, 7, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);