解析在Android中为TextView增加自定义HTML标签的实现方法

前端技术 2023/09/06 Android

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：

复制代码 代码如下:

/**
    * 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); 

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：

复制代码 代码如下:

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：

复制代码 代码如下:

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。

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