获取PackageManager对象
PackageManager packageManager = getActivity().getPackageManager();
ResolveInfo
Intent过滤器的返回值，通常记录了 AndroidManifest.xml 中的相关标签。
获取符合隐式Intent的最优Activity
resolveActivity返回的是ResolveInfo对象。
if (packageManager.resolveActivity(/* Intent */, PackageManager.MATCH_DEFAULT_ONLY) == null) {
// 不存在与隐式Inten对应的Activity
}
获取所有符合隐式Intent的多个Activity
Intent startupIntent = new Intent(Intent.ACTION_MAIN);
startupIntent.addCategory(Intent.CATEGORY_LAUNCHER);
List<ResolveInfo> activities = packageManager.queryIntentActivities(startupIntent, PackageManager.MATCH_DEFAULT_ONLY);
载入ResolveInfo对象的标签
mResolveInfo是与符合过滤器Intent.ACTION_MAIN的Activity相对应的，所以此处的Label通常是应用名字。
PackageManager packageManager = getActivity().getPackageManager();
String appName = mResolveInfo.loadLabel(packageManager).toString();
