Android開發教程：View Tag 的使用

發現Tag在View中還是很有作用的屬性，API中這樣描述的：

Tags

Unlike IDs, tags are not used to identify views. Tags are essentially an extra piece of information that can be associated with a view. They are most often used as a convenience to store data related to views in the views themselves rather than by putting them in a separate structure.

Tag不像ID是用標示view的。Tag從本質上來講是就是相關聯的view的額外的信息。它們經常用來存儲一些view的數據，這樣做非常方便而不用存入另外的單獨結構。

下面這個例子是從eoe中看到的，給我很大啟發：

1. public class FileListAdapter extends BaseAdapter {
5. private LayoutInflater mInflater;
7. private Bitmap mIcon_folder;
9. private Bitmap mIcon_file;
11. private Bitmap mIcon_image;
13. private Bitmap mIcon_audio;
15. private Bitmap mIcon_video;
17. private Bitmap mIcon_apk;
19. private List<String> items;
21. private List<String> paths;
23. private List<String> sizes;
25. private int isZoom = 0;
29. // MyAdapter的構造器
31. public FileListAdapter(Context context, List<String> it, List<String> pa,
33. List<String> si, int zm) {
35. mInflater = LayoutInflater.from(context);
37. items = it;
39. paths = pa;
41. sizes = si;
43. isZoom = zm;
45. mIcon_folder = BitmapFactory.decodeResource(context.getResources(),
47. R.drawable.folder); // 文件夾的圖標
49. mIcon_file = BitmapFactory.decodeResource(context.getResources(),
51. R.drawable.file); // 文件的圖文件
53. mIcon_image = BitmapFactory.decodeResource(context.getResources(),
55. R.drawable.image); // 圖片的圖文件
57. mIcon_audio = BitmapFactory.decodeResource(context.getResources(),
59. R.drawable.audio); // 音頻的圖文件
61. mIcon_video = BitmapFactory.decodeResource(context.getResources(),
63. R.drawable.video); // 視頻的圖文件
65. mIcon_apk = BitmapFactory.decodeResource(context.getResources(),
67. R.drawable.apk); // apk文件
69. }
73. @Override
75. public int getCount() {
77. return items.size();
79. }
83. @Override
85. public Object getItem(int position) {
87. return items.get(position);
89. }
93. @Override
95. public long getItemId(int position) {
97. return position;
99. }
103. @Override
105. public View getView(int position, View convertView, ViewGroup par) {
107. Bitmap bitMap = null;
109. ViewHolder holder = null;
111. if (convertView == null) {
113. // 使用自定義的list_items作為Layout
115. convertView = mInflater.inflate(R.layout.file_list_items, null);
117. // 初始化holder的text與icon
119. holder = new ViewHolder();
121. holder.f_title = ((TextView) convertView.findViewById(R.id.f_title));
123. holder.f_text = ((TextView) convertView.findViewById(R.id.f_text));
125. holder.f_icon = ((ImageView) convertView.findViewById(R.id.f_icon));
127. convertView.setTag(holder);
129. } else {
131. holder = (ViewHolder) convertView.getTag();
133. }
135. File f = new File(paths.get(position).toString());
137. // 設置文件或文件夾的文字與icon
139. holder.f_title.setText(f.getName());
141. String f_type = MyUtil.getMIMEType(f, false);
143. if (f.isDirectory()) {
145. holder.f_icon.setImageBitmap(mIcon_folder);
147. holder.f_text.setText("");
149. } else {
151. holder.f_text.setText(sizes.get(position));
153. if ("image".equals(f_type)) {
155. if (isZoom == 1) {
157. bitMap = MyUtil.fitSizePic(f);
159. if (bitMap != null) {
161. holder.f_icon.setImageBitmap(bitMap);
163. } else {
165. holder.f_icon.setImageBitmap(mIcon_image);
167. }
169. } else {
171. holder.f_icon.setImageBitmap(mIcon_image);
173. }
175. bitMap = null;
177. } else if ("audio".equals(f_type)) {
179. holder.f_icon.setImageBitmap(mIcon_audio);
181. } else if ("video".equals(f_type)) {
183. holder.f_icon.setImageBitmap(mIcon_video);
185. } else if ("apk".equals(f_type)) {
187. holder.f_icon.setImageBitmap(mIcon_apk);
189. } else {
191. holder.f_icon.setImageBitmap(mIcon_file);
193. }
195. }
197. return convertView;
199. }
203. /**
205. * 不單獨寫get set可以提高效率 class ViewHolder
207. * */
209. private class ViewHolder {
211. TextView f_title;
213. TextView f_text;
215. ImageView f_icon;
217. }
219. }