解析在Android中为TextView增加自定义HTML标签的实现方法

android中的textview，本身就支持部分的html格式标签。这其中包括常用的字体大小颜色设置，文本链接等。使用起来也比较方便，只需要使用html类转换一下即可。比如：

textview.settext(html.fromhtml(str));

然而，有一种场合，默认支持的标签可能不够用。比如，我们需要在textview中点击某种链接，返回到应用中的某个界面，而不仅仅是网络连接，如何实现？

经过几个小时对android中的html类源代码的研究，找到了解决办法，并且测试通过。

先看html类的源代码中有这样一段：

/**
    * is notified when html tags are encountered that the parser does
    * not know how to interpret.
    */ 
   public static interface taghandler { 
       /**
        * this method will be called whenn the html parser encounters
        * a tag that it does not know how to interpret.
        */ 
       public void handletag(boolean opening, string tag, 
                                editable output, xmlreader xmlreader); 

这里定义了一个接口，接口用于什么呢？

再继续看代码，看到对html的tag进行解析部分的代码：

private void handlestarttag(string tag, attributes attributes) { 
        if (tag.equalsignorecase("br")) { 
            // we don't need to handle this. tagsoup will ensure that there's a </br> for each <br>  
            // so we can safely emite the linebreaks when we handle the close tag.  
        } else if (tag.equalsignorecase("p")) { 
            handlep(mspannablestringbuilder); 
        } else if (tag.equalsignorecase("div")) { 
            handlep(mspannablestringbuilder); 
        } else if (tag.equalsignorecase("em")) { 
            start(mspannablestringbuilder, new bold()); 
        } else if (tag.equalsignorecase("b")) { 
            start(mspannablestringbuilder, new bold()); 
        } else if (tag.equalsignorecase("strong")) { 
            start(mspannablestringbuilder, new italic()); 
        } else if (tag.equalsignorecase("cite")) { 
            start(mspannablestringbuilder, new italic()); 
        } else if (tag.equalsignorecase("dfn")) { 
            start(mspannablestringbuilder, new italic()); 
        } else if (tag.equalsignorecase("i")) { 
            start(mspannablestringbuilder, new italic()); 
        } else if (tag.equalsignorecase("big")) { 
            start(mspannablestringbuilder, new big()); 
        } else if (tag.equalsignorecase("small")) { 
            start(mspannablestringbuilder, new small()); 
        } else if (tag.equalsignorecase("font")) { 
            startfont(mspannablestringbuilder, attributes); 
        } else if (tag.equalsignorecase("blockquote")) { 
            handlep(mspannablestringbuilder); 
            start(mspannablestringbuilder, new blockquote()); 
        } else if (tag.equalsignorecase("tt")) { 
            start(mspannablestringbuilder, new monospace()); 
        } else if (tag.equalsignorecase("a")) { 
            starta(mspannablestringbuilder, attributes); 
        } else if (tag.equalsignorecase("u")) { 
            start(mspannablestringbuilder, new underline()); 
        } else if (tag.equalsignorecase("sup")) { 
            start(mspannablestringbuilder, new super()); 
        } else if (tag.equalsignorecase("sub")) { 
            start(mspannablestringbuilder, new sub()); 
        } else if (tag.length() == 2 && 
                   character.tolowercase(tag.charat(0)) == 'h' && 
                   tag.charat(1) >= '1' && tag.charat(1) <= '6') { 
            handlep(mspannablestringbuilder); 
            start(mspannablestringbuilder, new header(tag.charat(1) - '1')); 
        } else if (tag.equalsignorecase("img")) { 
            startimg(mspannablestringbuilder, attributes, mimagegetter); 
        } else if (mtaghandler != null) { 
            mtaghandler.handletag(true, tag, mspannablestringbuilder, mreader); 
        } 
    } 

    private void handleendtag(string tag) { 
        if (tag.equalsignorecase("br")) { 
            handlebr(mspannablestringbuilder); 
        } else if (tag.equalsignorecase("p")) { 
            handlep(mspannablestringbuilder); 
        } else if (tag.equalsignorecase("div")) { 
            handlep(mspannablestringbuilder); 
        } else if (tag.equalsignorecase("em")) { 
            end(mspannablestringbuilder, bold.class, new stylespan(typeface.bold)); 
        } else if (tag.equalsignorecase("b")) { 
            end(mspannablestringbuilder, bold.class, new stylespan(typeface.bold)); 
        } else if (tag.equalsignorecase("strong")) { 
            end(mspannablestringbuilder, italic.class, new stylespan(typeface.italic)); 
        } else if (tag.equalsignorecase("cite")) { 
            end(mspannablestringbuilder, italic.class, new stylespan(typeface.italic)); 
        } else if (tag.equalsignorecase("dfn")) { 
            end(mspannablestringbuilder, italic.class, new stylespan(typeface.italic)); 
        } else if (tag.equalsignorecase("i")) { 
            end(mspannablestringbuilder, italic.class, new stylespan(typeface.italic)); 
        } else if (tag.equalsignorecase("big")) { 
            end(mspannablestringbuilder, big.class, new relativesizespan(1.25f)); 
        } else if (tag.equalsignorecase("small")) { 
            end(mspannablestringbuilder, small.class, new relativesizespan(0.8f)); 
        } else if (tag.equalsignorecase("font")) { 
            endfont(mspannablestringbuilder); 
        } else if (tag.equalsignorecase("blockquote")) { 
            handlep(mspannablestringbuilder); 
            end(mspannablestringbuilder, blockquote.class, new quotespan()); 
        } else if (tag.equalsignorecase("tt")) { 
            end(mspannablestringbuilder, monospace.class, 
                    new typefacespan("monospace")); 
        } else if (tag.equalsignorecase("a")) { 
            enda(mspannablestringbuilder); 
        } else if (tag.equalsignorecase("u")) { 
            end(mspannablestringbuilder, underline.class, new underlinespan()); 
        } else if (tag.equalsignorecase("sup")) { 
            end(mspannablestringbuilder, super.class, new superscriptspan()); 
        } else if (tag.equalsignorecase("sub")) { 
            end(mspannablestringbuilder, sub.class, new subscriptspan()); 
        } else if (tag.length() == 2 && 
                character.tolowercase(tag.charat(0)) == 'h' && 
                tag.charat(1) >= '1' && tag.charat(1) <= '6') { 
            handlep(mspannablestringbuilder); 
            endheader(mspannablestringbuilder); 
        } else if (mtaghandler != null) { 
            mtaghandler.handletag(false, tag, mspannablestringbuilder, mreader); 
        } 
    } 

可以看到，如果不是默认的标签，会调用mtaghandler的handletag方法。所以，我们可以实现此接口，来解析自己定义的标签类型。

再看一段我实现的对<game>标签进行解析的示例代码：

public class gametaghandler implements taghandler { 
    private int startindex = 0; 
    private int stopindex = 0; 
    @override 
    public void handletag(boolean opening, string tag, editable output, 
            xmlreader xmlreader) { 
        if (tag.tolowercase().equals("game")) { 
            if (opening) { 
                startgame(tag, output, xmlreader); 
            } else { 
                endgame(tag, output, xmlreader); 
            } 
        }  

    } 
    public void startgame(string tag, editable output, xmlreader xmlreader) { 
        startindex = output.length(); 
    } 

    public void endgame(string tag, editable output, xmlreader xmlreader) { 
        stopindex = output.length(); 
        output.setspan(new gamespan(), startindex, stopindex, 
                    spanned.span_exclusive_exclusive); 
    } 

    private class gamespan extends clickablespan implements onclicklistener { 

        @override 
        public void onclick(view v) { 
            // 跳转某页面  
        } 
    }

上面这段代码，是对<game>…</game>的自定义标签进行解析。

具体调用方法：

       textview.settext(html.fromhtml(“点击<game>这里</game>跳转到游戏”,

              null, new gametaghandler()));

       textview.setclickable(true);

       textview.setmovementmethod(linkmovementmethod.getinstance());

运行后，能够看到文本中的字符串“这里”带了超链接，点击链接后，gamespan类的onclick()方法被调用。就可以在这个方法中进行跳转了。