释放双眼，带上耳机，听听看~！
一、需求简介
Android中TextView可以实现简单的HTML解析，将Html文本封装为Spannable数据实现图文混排等富文本效果，但是同样问题很多。
1、SDK中提供的解析能力不够强，提供的样式支持不足，对于css属性的解析很弱。
2、不支持多个css样式同时解析。
3、SDK中提供的Html.TagHandler无法获取到标签属性。
4、可扩展性不够强，无法自定义解析器。
二、解决方案
方案1： 自定义一套HTML解析器，其实很简单，复制一份android.text.Html，替换其中SDK隐藏的XmlReader即可
方案2：移花接木，通过Html.TagHandler夺取解析流程控制权，然后获得拦截解析tag的能力。
这两种方案实质上都是可行的，第一种的话要实现自己的SaxParse解析，但工作量不小，因此这里我们主要提供方案二的实现方式。
三、移花接木
之所以可以移花接木，是因为TagHandler会被作为Html中标签解析的最后一个流程语句，当遇到自定义的或者Html类无法解析的标签，标签调用TagHandler的handleTag方法会被回调，同时可以获得TagName,Editable,XmlReader，然后我们便可移花接木。
package com.example.myapplication;
import android.graphics.drawable.Drawable;
import android.support.v4.util.ArrayMap;
import android.text.Editable;
import android.text.Html;
import android.util.Log;
import com.example.myapplication.tags.HtmlTag;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
public class HtmlTagHandler implements Html.TagHandler,Html.ImageGetter, ContentHandler {
private static final String LOG_TAG = "HtmlTagHandler";
private final String H5_TAG = "html"; //自定义标签，该标签无法在原Html类中解析
private volatile ContentHandler orginalContentHandler;
private int count = 0; //防止自定义的相互嵌套的情况 如：<html><html></html></html>
//设置标签计数器，防止自定义标签嵌套自定义标签
private XMLReader originalXmlReader;
private Editable originlaEditableText; //该对象是SpannableStringBuilder
private List<String> orginalTags = null;
//自定义解析器集合
private final Map<String,HtmlTag> tagHandlerMap;
public HtmlTagHandler( ) {
String orginalContentHandlerTag = "br|p|ul|li|div|span|strong|b|em|cite|dnf|i|big|small|font|blockquote|tt|a|u|del|s|strike|sup|sub|h1|h2|h3|h4|h5|h6|img";
//原android.text.Html类中可以解析的标签
orginalTags = Arrays.asList(orginalContentHandlerTag.split("|"));
tagHandlerMap = new ArrayMap<>();
}
//注册解析器
public void registerTag(String tagName,HtmlTag tagHandler){
tagHandlerMap.put(tagName,tagHandler);
}
public HtmlTag unregisterTag(String tagName){
return tagHandlerMap.remove(tagName);
}
@Override
public Drawable getDrawable(String source) {
return null;
}
//处理原Html中无法识别的标签
@Override
public void handleTag(boolean opening, String tag, Editable output, XMLReader xmlReader) {
if(opening){
startHandleTag(tag,output,xmlReader);
}else{
endHandleTag(tag,output,xmlReader);
}
}
private void startHandleTag( String tag, Editable output, XMLReader xmlReader) {
if (tag.equalsIgnoreCase(H5_TAG)){
if(orginalContentHandler==null) {
orginalContentHandler = xmlReader.getContentHandler();
this.originalXmlReader = xmlReader; //获取XmlReader
this.originalXmlReader.setContentHandler(this);//获取控制权,让本类监听解析流程
this.originlaEditableText = output; //获取到SpannableStringBuilder
}
count++;
}
}
private void endHandleTag( String tag, Editable output, XMLReader xmlReader) {
if(tag.equalsIgnoreCase(tag)){
count--;
if(count==0 ){
this.originalXmlReader.setContentHandler(this.orginalContentHandler);
//将原始的handler交还
this.originalXmlReader = null;
this.originlaEditableText = null;
this.orginalContentHandler = null;
//还原控制权
}
}
}
@Override
public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {
if (localName.equalsIgnoreCase(H5_TAG)){
handleTag(true,localName,this.originlaEditableText,this.originalXmlReader);
}else if(canHandleTag(localName)){ //拦截，判断是否可以解析该标签
final HtmlTag htmlTag = tagHandlerMap.get(localName); //读取自定义解析器开始解析
htmlTag.startHandleTag(this.originlaEditableText,atts);
}else if(orginalTags.contains(localName)){ //无法解析的优先让原Html类解析
this.orginalContentHandler.startElement(uri,localName,qName,atts);
}else{
Log.e(LOG_TAG,"无法解析的标签<"+localName+">");
}
}
private boolean canHandleTag(String tagName) {
if(!tagHandlerMap.containsKey(tagName)){
return false;
}
final HtmlTag htmlTag = tagHandlerMap.get(tagName);
return htmlTag!=null;
}
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
if (localName.equalsIgnoreCase(H5_TAG)){
handleTag(false,localName,this.originlaEditableText,this.originalXmlReader);
}else if(canHandleTag(localName)){
final HtmlTag htmlTag = tagHandlerMap.get(localName); //读取自定义解析器结束解析
htmlTag.endHandleTag(this.originlaEditableText);
}else if(orginalTags.contains(localName)){
this.orginalContentHandler.endElement(uri,localName,qName);
}else{
Log.e(LOG_TAG,"无法解析的标签</"+localName+">");
}
}
@Override
public void characters(char[] ch, int start, int length) throws SAXException {
orginalContentHandler.characters(ch,start,length);
}
@Override
public void ignorableWhitespace(char[] ch, int start, int length) throws SAXException {
orginalContentHandler.ignorableWhitespace(ch,start,length);
}
@Override
public void processingInstruction(String target, String data) throws SAXException {
orginalContentHandler.processingInstruction(target,data);
}
@Override
public void skippedEntity(String name) throws SAXException {
orginalContentHandler.skippedEntity(name);
}
@Override
public void setDocumentLocator(Locator locator) {
orginalContentHandler.setDocumentLocator(locator);
}
@Override
public void startDocument() throws SAXException {
orginalContentHandler.startDocument();
}
@Override
public void endDocument() throws SAXException {
orginalContentHandler.endDocument();
}
@Override
public void startPrefixMapping(String prefix, String uri) throws SAXException {
orginalContentHandler.startPrefixMapping(prefix,uri);
}
@Override
public void endPrefixMapping(String prefix) throws SAXException {
orginalContentHandler.endPrefixMapping(prefix);
}
}
以上TagHandler就实现了，接下来实现自己的解析器，为了更好的约束定义规则，我们这里实现一个抽象类，并提供一些解析工具。
public abstract class HtmlTag {
private Context context;
public HtmlTag(Context context) {
this.context = context;
}
public Context getContext() {
return context;
}
private static final Map<String, Integer> sColorNameMap;
static {
sColorNameMap = new ArrayMap<String, Integer>();
sColorNameMap.put("black", Color.BLACK);
sColorNameMap.put("darkgray", Color.DKGRAY);
sColorNameMap.put("gray", Color.GRAY);
sColorNameMap.put("lightgray", Color.LTGRAY);
sColorNameMap.put("white", Color.WHITE);
sColorNameMap.put("red", Color.RED);
sColorNameMap.put("green", Color.GREEN);
sColorNameMap.put("blue", Color.BLUE);
sColorNameMap.put("yellow", Color.YELLOW);
sColorNameMap.put("cyan", Color.CYAN);
sColorNameMap.put("magenta", Color.MAGENTA);
sColorNameMap.put("aqua", 0xFF00FFFF);
sColorNameMap.put("fuchsia", 0xFFFF00FF);
sColorNameMap.put("darkgrey", Color.DKGRAY);
sColorNameMap.put("grey", Color.GRAY);
sColorNameMap.put("lightgrey", Color.LTGRAY);
sColorNameMap.put("lime", 0xFF00FF00);
sColorNameMap.put("maroon", 0xFF800000);
sColorNameMap.put("navy", 0xFF000080);
sColorNameMap.put("olive", 0xFF808000);
sColorNameMap.put("purple", 0xFF800080);
sColorNameMap.put("silver", 0xFFC0C0C0);
sColorNameMap.put("teal", 0xFF008080);
sColorNameMap.put("white", Color.WHITE);
sColorNameMap.put("transparent", Color.TRANSPARENT);
}
@ColorInt
public static int getHtmlColor(String colorString){
if(sColorNameMap.containsKey(colorString.toLowerCase())){
Integer colorInt = sColorNameMap.get(colorString);
if(colorInt!=null) return colorInt;
}
return parseHtmlColor(colorString.toLowerCase());
}
@ColorInt
public static int parseHtmlColor( String colorString) {
if (colorString.charAt(0) == '#') {
if(colorString.length()==4){
StringBuilder sb = new StringBuilder("#");
for (int i=1;i<colorString.length();i++){
char c = colorString.charAt(i);
sb.append(c).append(c);
}
colorString = sb.toString();
}
long color = Long.parseLong(colorString.substring(1), 16);
if (colorString.length() == 7) {
// Set the alpha value
color |= 0x00000000ff000000;
} else if (colorString.length() != 9) {
throw new IllegalArgumentException("Unknown color");
}
return (int)color;
} else if(colorString.startsWith("rgb(") || colorString.startsWith("rgba(") && colorString.endsWith(")")){
colorString = colorString.substring(colorString.indexOf("("),colorString.indexOf(")"));
colorString = colorString.replaceAll(" ","");
String[] colorArray = colorString.split(",");
if(colorArray.length==3){
return Color.argb(255,Integer.parseInt(colorArray[0]),Integer.parseInt(colorArray[1]),Integer.parseInt(colorArray[2]));
}
else if (colorArray.length==4){
return Color.argb(Integer.parseInt(colorArray[3]),Integer.parseInt(colorArray[0]),Integer.parseInt(colorArray[1]),Integer.parseInt(colorArray[2]));
}
}
throw new IllegalArgumentException("Unknown color");
}
public static <T> T getLast(Spanned text, Class<T> kind) {
T[] objs = text.getSpans(0, text.length(), kind);
if (objs.length == 0) {
return null;
} else {
return objs[objs.length - 1];
}
}
public abstract void startHandleTag(Editable text, Attributes attributes); //开始解析
public abstract void endHandleTag(Editable text); //结束解析
}
实际上，到这里我们的任务已经完成了，按照规则实现解析即可。startHandleTag和endHandleTag因为参数Editable本质上就是SpannableStringBuilder类，同时提供了attributes，接下来的工作无非就是Editable.setSpan的操作，接下来看一个案例。
四、案例：改写span标签的解析规则
public class SpanTag extends HtmlTag{
private static Pattern sTextDecorationPattern;
private static Pattern sBackgroundColorPattern;
private static Pattern sForegroundColorPattern;
public SpanTag(Context context) {
super(context);
}
private int getHtmlSize(String fontSize) {
fontSize = fontSize.toLowerCase();
if(fontSize.endsWith("px")){
return (int) Double.parseDouble(fontSize.substring(0,fontSize.indexOf("px")));
}else if(fontSize.endsWith("sp") ){
float sp = (float) Double.parseDouble(fontSize.substring(0,fontSize.indexOf("sp")));
return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,sp,getContext().getResources().getDisplayMetrics());
}else if(TextUtils.isDigitsOnly(fontSize)){ //如果不带单位，默认按照sp处理
float sp = (float) Double.parseDouble(fontSize);
return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,sp,getContext().getResources().getDisplayMetrics());
}
return -1;
}
private static String getTextColorPattern(String style) {
String cssName = "text-color";
String cssVal = getHtmlCssValue(style, cssName);
if(TextUtils.isEmpty(cssVal)){
cssName = "color";
cssVal = getHtmlCssValue(style, cssName);
}
return cssVal;
}
@Nullable
private static String getHtmlCssValue(String style, String cssName) {
final String[] keyValueSet = style.split(";");
if(keyValueSet==null) return null;
for (int i=0;i<keyValueSet.length;i++){
final String match = keyValueSet[i].replaceAll(" ","").toLowerCase();
if(match.indexOf(cssName)==0){
final String[] parts = match.split(":");
if(parts==null || parts.length!=2) continue;
return parts[1];
}
}
return null;
}
private static String getBackgroundColorPattern(String style) {
String cssName = "background-color";
String cssVal = getHtmlCssValue(style, cssName);
if(TextUtils.isEmpty(cssVal)){
cssName = "bakground";
cssVal = getHtmlCssValue(style, cssName);
}
return cssVal;
}
private static String getTextFontSizePattern(String style) {
String cssName = "font-size";
String cssVal = getHtmlCssValue(style, cssName);
return cssVal;
}
public static class Font{ //定义标记
int textSize;
public Font( int textSize) {
this.textSize = textSize;
}
}
public static class Background{ //定义标记
int color;
public Background(int color) {
this.color = color;
}
}
@Override
public void startHandleTag(Editable text, Attributes attributes) {
String style = attributes.getValue("", "style");
if(TextUtils.isEmpty(style)) return;
int textSize = -1;
String textColorPattern = getTextColorPattern(style);
if (!TextUtils.isEmpty(textColorPattern)) {
int c = getHtmlColor(textColorPattern);
c = c | 0xFF000000;
start(text,new ForegroundColorSpan(c));
}
String fontSizePattern = getTextFontSizePattern(style);
if(!TextUtils.isEmpty(fontSizePattern)){
textSize = getHtmlSize(fontSizePattern);
}
if(textSize!=-1){
start(text,new Font(textSize)); //注意，第二个参数可以为任意Object类型，这里起到标记的作用
}
String backgroundColorPattern = getBackgroundColorPattern(style);
if (!TextUtils.isEmpty(backgroundColorPattern)) {
int c = getHtmlColor(backgroundColorPattern);
c = c | 0xFF000000;
start(text,new Background(c));
}
}
@Override
public void endHandleTag(Editable text){
Background b = getLast(text, Background.class); //读取出最后标记类型
if(b!=null){
end(text,Background.class,new BackgroundColorSpan(b.color)); //设置为Android可以解析的24种ParcelableSpan基本分类，当然也可以自己定义，但需要集成原有的分类
}
final ForegroundColorSpan fc = getLast(text, ForegroundColorSpan.class);
if(fc!=null){
end(text,Font.class,new ForegroundColorSpan(fc.getForegroundColor()));
}
Font f = getLast(text, Font.class);
if (f != null) {
end(text,Font.class,new TextFontSpan(f.textSize)); //使用自定义的
}
}
private static void start(Editable text, Object mark) {
int len = text.length();
text.setSpan(mark, len, len, Spannable.SPAN_INCLUSIVE_EXCLUSIVE); //添加标记在最后一位，注意开始位置和结束位置
}
@SuppressWarnings("unchecked")
private static void end(Editable text, Class kind, Object repl) {
Object obj = getLast(text, kind); //读取kind类型
if (obj != null) {
setSpanFromMark(text, obj, repl);
}
}
private static void setSpanFromMark(Spannable text, Object mark, Object... spans) {
int where = text.getSpanStart(mark);
text.removeSpan(mark);
//移除原有标记，因为原有标记不是默认的24种ParcelableSpan子类，因此无法渲染文本
int len = text.length();
if (where != len) {
for (Object span : spans) {
text.setSpan(span, where, len, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE); //注意：开始位置和结束位置，因为SpannableStringBuilder的append添加字符方法导致len已经大于where了
}
}
}
}
关于TextFont实现很简单，代码如下
public class TextFontSpan extends AbsoluteSizeSpan {
private int color;
public TextFontSpan(int size) {
this(size,false);
//这里我们以px作为单位，方便统一调用
}
/**
* 保持构造方法无法被外部调用
* @param size
* @param dip
*/
protected TextFontSpan(int size, boolean dip) {
super(size, dip);
}
public TextFontSpan(Parcel src) {
super(src);
}
}
使用方法：
HtmlTagHandler htmlTagHandler = new HtmlTagHandler();
htmlTagHandler.registerTag("span",new SpanTag(targetFragment.getContext()));
String source = "<html>今天<span style='color:#FFE31335;font-size:16sp;background-color:white;'>星期三</span>，<span style='color:#fff;font-size:14sp;background-color:red;'>但是我还要加班</span><html>";
final Spanned spanned = Html.fromHtml(source, htmlTagHandler, htmlTagHandler);
textView.setText(spanned );注意: <html>标签必须加到要解析的文本段，否则Android系统仍然会走Html的解析流程。