Android中為TextView增加自定義的HTML標簽

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：

1. /**
2. * Is notified when HTML tags are encountered that the parser does
3. * not know how to interpret.
4. */
5. public static interface TagHandler {
6. /**
7. * This method will be called whenn the HTML parser encounters
8. * a tag that it does not know how to interpret.
9. */
10. public void handleTag(boolean opening, String tag,
11. 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：

1. private void handleStartTag(String tag, Attributes attributes) {
2. if (tag.equalsIgnoreCase("br")) {
3. // We don't need to handle this. TagSoup will ensure that there's a </br> for each <br>
4. // so we can safely emite the linebreaks when we handle the close tag.
5. } else if (tag.equalsIgnoreCase("p")) {
6. handleP(mSpannableStringBuilder);
7. } else if (tag.equalsIgnoreCase("div")) {
8. handleP(mSpannableStringBuilder);
9. } else if (tag.equalsIgnoreCase("em")) {
10. start(mSpannableStringBuilder, new Bold());
11. } else if (tag.equalsIgnoreCase("b")) {
12. start(mSpannableStringBuilder, new Bold());
13. } else if (tag.equalsIgnoreCase("strong")) {
14. start(mSpannableStringBuilder, new Italic());
15. } else if (tag.equalsIgnoreCase("cite")) {
16. start(mSpannableStringBuilder, new Italic());
17. } else if (tag.equalsIgnoreCase("dfn")) {
18. start(mSpannableStringBuilder, new Italic());
19. } else if (tag.equalsIgnoreCase("i")) {
20. start(mSpannableStringBuilder, new Italic());
21. } else if (tag.equalsIgnoreCase("big")) {
22. start(mSpannableStringBuilder, new Big());
23. } else if (tag.equalsIgnoreCase("small")) {
24. start(mSpannableStringBuilder, new Small());
25. } else if (tag.equalsIgnoreCase("font")) {
26. startFont(mSpannableStringBuilder, attributes);
27. } else if (tag.equalsIgnoreCase("blockquote")) {
28. handleP(mSpannableStringBuilder);
29. start(mSpannableStringBuilder, new Blockquote());
30. } else if (tag.equalsIgnoreCase("tt")) {
31. start(mSpannableStringBuilder, new Monospace());
32. } else if (tag.equalsIgnoreCase("a")) {
33. startA(mSpannableStringBuilder, attributes);
34. } else if (tag.equalsIgnoreCase("u")) {
35. start(mSpannableStringBuilder, new Underline());
36. } else if (tag.equalsIgnoreCase("sup")) {
37. start(mSpannableStringBuilder, new Super());
38. } else if (tag.equalsIgnoreCase("sub")) {
39. start(mSpannableStringBuilder, new Sub());
40. } else if (tag.length() == 2 &&
41. Character.toLowerCase(tag.charAt(0)) == 'h' &&
42. tag.charAt(1) >= '1' && tag.charAt(1) <= '6') {
43. handleP(mSpannableStringBuilder);
44. start(mSpannableStringBuilder, new Header(tag.charAt(1) - '1'));
45. } else if (tag.equalsIgnoreCase("img")) {
46. startImg(mSpannableStringBuilder, attributes, mImageGetter);
47. } else if (mTagHandler != null) {
48. mTagHandler.handleTag(true, tag, mSpannableStringBuilder, mReader);
49. }
50. }
52. private void handleEndTag(String tag) {
53. if (tag.equalsIgnoreCase("br")) {
54. handleBr(mSpannableStringBuilder);
55. } else if (tag.equalsIgnoreCase("p")) {
56. handleP(mSpannableStringBuilder);
57. } else if (tag.equalsIgnoreCase("div")) {
58. handleP(mSpannableStringBuilder);
59. } else if (tag.equalsIgnoreCase("em")) {
60. end(mSpannableStringBuilder, Bold.class, new StyleSpan(Typeface.BOLD));
61. } else if (tag.equalsIgnoreCase("b")) {
62. end(mSpannableStringBuilder, Bold.class, new StyleSpan(Typeface.BOLD));
63. } else if (tag.equalsIgnoreCase("strong")) {
64. end(mSpannableStringBuilder, Italic.class, new StyleSpan(Typeface.ITALIC));
65. } else if (tag.equalsIgnoreCase("cite")) {
66. end(mSpannableStringBuilder, Italic.class, new StyleSpan(Typeface.ITALIC));
67. } else if (tag.equalsIgnoreCase("dfn")) {
68. end(mSpannableStringBuilder, Italic.class, new StyleSpan(Typeface.ITALIC));
69. } else if (tag.equalsIgnoreCase("i")) {
70. end(mSpannableStringBuilder, Italic.class, new StyleSpan(Typeface.ITALIC));
71. } else if (tag.equalsIgnoreCase("big")) {
72. end(mSpannableStringBuilder, Big.class, new RelativeSizeSpan(1.25f));
73. } else if (tag.equalsIgnoreCase("small")) {
74. end(mSpannableStringBuilder, Small.class, new RelativeSizeSpan(0.8f));
75. } else if (tag.equalsIgnoreCase("font")) {
76. endFont(mSpannableStringBuilder);
77. } else if (tag.equalsIgnoreCase("blockquote")) {
78. handleP(mSpannableStringBuilder);
79. end(mSpannableStringBuilder, Blockquote.class, new QuoteSpan());
80. } else if (tag.equalsIgnoreCase("tt")) {
81. end(mSpannableStringBuilder, Monospace.class,
82. new TypefaceSpan("monospace"));
83. } else if (tag.equalsIgnoreCase("a")) {
84. endA(mSpannableStringBuilder);
85. } else if (tag.equalsIgnoreCase("u")) {
86. end(mSpannableStringBuilder, Underline.class, new UnderlineSpan());
87. } else if (tag.equalsIgnoreCase("sup")) {
88. end(mSpannableStringBuilder, Super.class, new SuperscriptSpan());
89. } else if (tag.equalsIgnoreCase("sub")) {
90. end(mSpannableStringBuilder, Sub.class, new SubscriptSpan());
91. } else if (tag.length() == 2 &&
92. Character.toLowerCase(tag.charAt(0)) == 'h' &&
93. tag.charAt(1) >= '1' && tag.charAt(1) <= '6') {
94. handleP(mSpannableStringBuilder);
95. endHeader(mSpannableStringBuilder);
96. } else if (mTagHandler != null) {
97. mTagHandler.handleTag(false, tag, mSpannableStringBuilder, mReader);
98. }
99. }