Android中为TextView增加自定义的HTML标签

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。