有用代码段2

1、ListView使用ViewHolder极简写法

	/**
	 * 在指定View中依据指定ID寻找控件(内置ViewHolder缓存)
	 * 
	 * @param convertView
	 *            容器
	 * @param id
	 *            控件ID
	 * @return 找到的控件
	 */
	@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;
	}

使用方法：

    @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、设置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>

说明：AppBaseTheme通常是你application指定的android:theme是啥这里就是啥。否则Activity内部的空间风格可能不一致。

用途：用于模拟Dialog效果。比方再Service中没法用Dialog，就能够用Activity来模拟

3、

	/**
	 * 获取设备上全部已安装并能够启动的应用的包名集合
	 * 
	 * @param context
	 *            上下文对象
	 * @return 满足条件的包名的集合
	 */
	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会返回非常多无法启动甚至没有图标的系统应用。