Android的TextView使用Html来处理图片显示、字体样式、超链接等

以下代码摘录至android源码里面的MMS项目，其中的

package com.android.mms.ui 里的 MessageListItem.java

package com.android.mms.util 里的 SmileyParser.java

/***
     * 
         * 此方法描述的是：   注意此方法在做表情转换的准备了
         * @author:wujun@cqghong.com,ppwuyi@sohu.com
         * @version: 2010-5-13 下午03:31:13
     */
    private void bindCommonMessage(final MessageItem msgItem) {
        if (mDownloadButton != null) {
            mDownloadButton.setVisibility(View.GONE);
            mDownloadingLabel.setVisibility(View.GONE);
        }
        // Since the message text should be concatenated with the sender‘s
        // address(or name), I have to display it here instead of
        // displaying it by the Presenter.
        mBodyTextView.setTransformationMethod(HideReturnsTransformationMethod.getInstance());

        // Get and/or lazily set the formatted message from/on the
        // MessageItem. Because the MessageItem instances come from a
        // cache (currently of size ~50), the hit rate on avoiding the
        // expensive formatMessage() call is very high.
        CharSequence formattedMessage = msgItem.getCachedFormattedMessage();
        if (formattedMessage == null) { //肯定为null应为msgItem.formattedMessage从诞生来就没被注意过一次
            formattedMessage = formatMessage(msgItem.mContact, msgItem.mBody,   //重点到了
                                             msgItem.mSubject, msgItem.mTimestamp,
                                             msgItem.mHighlight);
            msgItem.setCachedFormattedMessage(formattedMessage);
        }
        mBodyTextView.setText(formattedMessage);

        if (msgItem.isSms()) {
            hideMmsViewIfNeeded();
        } else {
            Presenter presenter = PresenterFactory.getPresenter(
                    "MmsThumbnailPresenter", mContext,
                    this, msgItem.mSlideshow);
            presenter.present();

            if (msgItem.mAttachmentType != WorkingMessage.TEXT) {
                inflateMmsView();
                mMmsView.setVisibility(View.VISIBLE);
                setOnClickListener(msgItem);
                drawPlaybackButton(msgItem);
            } else {
                hideMmsViewIfNeeded();
            }
        }

        drawLeftStatusIndicator(msgItem.mBoxId);
        drawRightStatusIndicator(msgItem);
    }
//------------------------------------------------------------------------------

/***
     * 
         * 此方法描述的是：   开始转换了哦
         * @author:wujun@cqghong.com,ppwuyi@sohu.com
         * @version: 2010-5-13 下午03:32:52
     */
    private CharSequence formatMessage(String contact, String body, String subject,
                                       String timestamp, String highlight) {
        CharSequence template = mContext.getResources().getText(R.string.name_colon); //遇到鬼了     &lt;主题：<xliff:g id="SUBJECT">%s</xliff:g>&gt;"
        SpannableStringBuilder buf =                   //把他当作StringBuffer只是它可以放的不是 String 而已他能放跟多类型的东西
            new SpannableStringBuilder(TextUtils.replace(template,
                new String[] { "%s" },
                new CharSequence[] { contact })); //替换成联系人

        boolean hasSubject = !TextUtils.isEmpty(subject); //主题
        if (hasSubject) {
            buf.append(mContext.getResources().getString(R.string.inline_subject, subject)); //buff先在是 联系人 主题 XXXX      eg wuyi <主题:dsadasdsa> 我爱我家
        }

        if (!TextUtils.isEmpty(body)) {
            if (hasSubject) {
                buf.append(" - "); //如果内容有主题有就+ " - "    eg wuyi <主题:sdsadsadsa> - 
            }
            SmileyParser parser = SmileyParser.getInstance(); //获得表情类了哦
            buf.append(parser.addSmileySpans(body)); //追查 急切关注中
        }
        if (!TextUtils.isEmpty(timestamp)) {
            buf.append("\n");
            int startOffset = buf.length();

            // put a one pixel high spacer line between the message and the time stamp as requested
            // by the spec.
            //把之间的信息和时间戳的要求间隔一个像素的高线
            //由规范
            buf.append("\n");
            buf.setSpan(new AbsoluteSizeSpan(3), startOffset, buf.length(),
                    Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

            startOffset = buf.length();
            buf.append(timestamp);
            buf.setSpan(new AbsoluteSizeSpan(12), startOffset, buf.length(),
                    Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
            // Make the timestamp text not as dark 改变某区域颜色   时间的地方为特殊颜色
            int color = mContext.getResources().getColor(R.color.timestamp_color);
            buf.setSpan(new ForegroundColorSpan(color), startOffset, buf.length(),
                    Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
        if (highlight != null) {
            int highlightLen = highlight.length();

            String s = buf.toString().toLowerCase();
            int prev = 0;
            while (true) {
                int index = s.indexOf(highlight, prev);
                if (index == -1) {
                    break;
                }
                buf.setSpan(new StyleSpan(Typeface.BOLD), index, index + highlightLen, 0);
                prev = index + highlightLen;
            }
        }
        return buf;
    }

//------------------------------------------------------------

/**
     * Adds ImageSpans to a CharSequence that replace textual emoticons such
     * as :-) with a graphical version.
     * 
     * @param text A CharSequence possibly containing emoticons
     * @return A CharSequence annotated with ImageSpans covering any
     *         recognized emoticons.
     * 添加ImageSpans一个CharSequence的表情符号代替文字等     *如用图形版本:-)。
     * 核心是把表情字符替换成ImageSpans的对象
     */
    public CharSequence addSmileySpans(CharSequence text) {
        SpannableStringBuilder builder = new SpannableStringBuilder(text);

        Matcher matcher = mPattern.matcher(text);
        while (matcher.find()) {
            int resId = mSmileyToRes.get(matcher.group());
            //注意下面的一块有点不好理解哦但是是核心
            builder.setSpan(new ImageSpan(mContext, resId), matcher.start(), matcher.end(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        }

        return builder;
    }

总结：

     android 在将字符转化为表情图像其核心代码为

builder.setSpan(new ImageSpan(mContext, resId), matcher.start(), matcher.end(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
原理过程是先匹配到表情字符然后通过new ImageSpan(上下文,表情地址)绘制出一个ImageView然后替换掉表情字符。

Android TextView 支持的HTML标签

• <a href="...">
• <b>
• <big>
• <blockquote>
• <br>
• <cite>
• <dfn>
• <div align="...">
• <em>
• <font size="..." color="..." face="...">
• <h1>
• <h2>
• <h3>
• <h4>
• <h5>
• <h6>
• <i>
• <img src="...">
• <p>
• <small>
• <strike>
• <strong>
• <sub>
• <sup>
• <tt>
• <u>