Question

是否有可能在AndroidManifest.xml中标记的自定义属性

Answer 1

Yes. Here's an example. The custom tag is ContentVersion.
<application android:name=".MyApplication"
android:icon="@drawable/icon"
android:label="@string/app_name">

<meta-data android:name="ContentVersion" android:value="1.9" />

<activity android:name="com.someone.something.MainActivity"
android:theme="@android:style/Theme.Translucent.NoTitleBar"
android:screenOrientation="sensor"
android:label="@string/app_name">

To access it:
ApplicationInfo ai = _context.getPackageManager().getApplicationInfo(_context.getPackageName(),PackageManager.GET_META_DATA);
ai.metaData.get("ContentVersion")