解析在Android中為TextView增加自定義HTML標簽的實現方法

Android中的TextView，本身就支持部分的Html格式標簽。這其中包括常用的字體大小顏色設置，文本鏈接等。使用起來也比較方便，只需要使用Html類轉換一下即可。比如：

textView.setText(Html.fromHtml(str));

然而，有一種場合，默認支持的標簽可能不夠用。比如，我們需要在textView中點擊某種鏈接，返回到應用中的某個界面，而不僅僅是網絡連接，如何實現？

經過幾個小時對android中的Html類源代碼的研究，找到了解決辦法，並且測試通過。

先看Html類的源代碼中有這樣一段：
代碼如下：

/**
    * 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); 

這裡定義了一個接口，接口用於什麼呢？

再繼續看代碼，看到對Html的tag進行解析部分的代碼：
代碼如下：

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，如果不是默認的標簽，會調用mTagHandler的handleTag方法。所以，我們可以實現此接口，來解析自己定義的標簽類型。

再看一段我實現的對<game>標簽進行解析的示例代碼：
代碼如下：

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) { 
            // 跳轉某頁面  
        } 
    }

上面這段代碼，是對<game>…</game>的自定義標簽進行解析。

具體調用方法：

       textView.setText(Html.fromHtml(“點擊<game>這裡</game>跳轉到游戲”,

              null, new GameTagHandler()));

       textView.setClickable(true);

       textView.setMovementMethod(LinkMovementMethod.getInstance());

運行後，能夠看到文本中的字符串“這裡”帶了超鏈接，點擊鏈接後，GameSpan類的onClick()方法被調用。就可以在這個方法中進行跳轉了。