解析在Android中為TextView增加自定義HTML標簽的實現方法

2020-04-11 12:25:13

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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，并且測試通過。

先看Html類的源代碼中有這樣一段：

復制代碼代碼如下:

/** 
    * 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);  

這里定義了一個接口，接口用于什么呢？

再繼續看代碼，看到對Html的tag進行解析部分的代碼：

復制代碼代碼如下:

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：

復制代碼代碼如下:

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   
        }  
    } 