ApplicationInfo,ResolveInfo,PackageManager

ApplicationInfo: Information you can retrieve about a particular application. This corresponds to information collected from the AndroidManifest.xml's application
                       根据AndroidManifest.xml文件中的标签“application” 检索到特定的应用，包含activity,broadcast,service,provider。

ResolveInfo:     Information that is returned from resolving an intent  against an IntentFilter. This partially corresponds to information collected from the AndroidManifest.xml's intent

                       根据AndroidManifest.xml文件中的标签“ intent” 检索到特定的应用。

PackageManager: Class for retrieving various kinds of information related to the application packages that are currently installed on the device.

                       这个类关联了所有已经安装在手机上的应用，可以利用这个类的对象获取上面两种信息。

代码：

PackageManager manager = getPackageManager();

//Return a List of all application packages that are installed on the  device. 获取所有已经安装的应用的信息。
List< ApplicationInfo> appList = manager.getInstalledApplications(PackageManager.GET.UNINSTALLED_PAKAGES);

// Retrieve all activities that can be performed for the given intent.仅仅是获取所有符合指定intent-filter的activity

Intent intent = new Intent(Intent.A CTION_MAIN,null);
intent.addCategory(Intent.CATEGORY_LAUNCHER);
List< ResolveInfo> activityList = manager.queryIntentActivities(intent,0);

拿到上面信息后，可以得到应用的icon ,label等。