實用程式碼片段2，實用程式碼片段

實用程式碼片段2，實用程式碼片段

1、ListView使用ViewHolder極簡寫法

/** * 在指定View中根據指定ID尋找控制項(內建ViewHolder緩衝) *  * @param convertView *            容器 * @param id *            控制項ID * @return 找到的控制項 */@SuppressWarnings("unchecked")public static <T extends View> T getAdapterView(View convertView, int id) {SparseArray<View> viewHolder = (SparseArray<View>) convertView.getTag();if (viewHolder == null) {viewHolder = new SparseArray<View>();convertView.setTag(viewHolder);}View childView = viewHolder.get(id);if (childView == null) {childView = convertView.findViewById(id);viewHolder.put(id, childView);}return (T) childView;}

用法：

    @Override    public View getView(int position, View convertView, ViewGroup parent) {        if (convertView == null) {            convertView = LayoutInflater.from(getActivity()).inflate(R.layout.fragment_feed_item, parent, false);        }        ImageView thumnailView = getAdapterView(convertView, R.id.video_thumbnail);        ImageView avatarView =  getAdapterView(convertView, R.id.user_avatar);        ImageView appIconView = getAdapterView(convertView, R.id.app_icon);

2、設定Activity透明

    <style name="TransparentActivity" parent="AppBaseTheme">        <item name="android:windowBackground">@android:color/transparent</item>        <item name="android:colorBackgroundCacheHint">@null</item>        <item name="android:windowIsTranslucent">true</item>        <item name="android:windowNoTitle">true</item>        <item name="android:windowContentOverlay">@null</item>    </style>

說明：AppBaseTheme一般是你application指定的android:theme是啥這裡就是啥，否則Activity內部的空間風格可能不一致。

用途：用於類比Dialog效果，比如再Service中沒法用Dialog，就可以用Activity來類比

3、

/** * 擷取裝置上所有已安裝並可以啟動的應用的包名集合 *  * @param context *            內容物件 * @return 滿足條件的包名的集合 */public static List<String> getAllCanOpenApp(Context context) {Intent intent = new Intent(Intent.ACTION_MAIN);intent.addCategory(Intent.CATEGORY_LAUNCHER);List<ResolveInfo> activities = context.getPackageManager().queryIntentActivities(intent, 0);if (DataUtil.isEmpty(activities)) {return null;}List<String> list = new ArrayList<String>();String packName;for (ResolveInfo info : activities) {packName=info.activityInfo.packageName;if(DataUtil.isEmpty(packName)){continue;}list.add(packName);}return list;}

使用getInstalledPackages會返回很多無法啟動甚至沒有表徵圖的系統應用。