Basic Android - 1

To make an Activity single-instance, use android:launchMode attribute in AndroidManifest.xml with value 'singleInstance' (or 'singleTask'). Multiprocess and TaskAffinity serve different purposes - they don't control instance creation.

The android:theme attribute in the tag sets the app's visual style (defines colors, fonts, widget styles). 'Style' refers to individual style resources applied to specific views, while 'ConfigChanges' controls configuration changes handling.

Environment.getExternalStorageDirectory() returns the File object representing the primary external storage directory. getExternalStorageState() returns storage state (mounted/shared/etc), and getExternalStoragePath() is not a standard Android API.

Pre-API 19, WRITE_EXTERNAL_STORAGE alone allowed both read and write. From API 19+, reading doesn't need permission. From API 23+, write permission requires runtime request. The correct answer depends on API level and use case - you may need either one or both depending on operation and Android version.

ImeOptions is the correct attribute used to configure the soft keyboard's action buttons (Next, Done, Search, etc.). inputMethod refers to the input method service itself, not button configuration. imeActionLabel only sets custom text labels but doesn't control button visibility. It is definitely possible through xml attribute android:imeOptions or programmatically.

adjustPan shifts the window contents upward to keep the focused field visible, which is what prevents the keyboard from covering the layout. stateUnvisible and stateVisible control keyboard visibility, not layout behavior. adjustResize resizes the layout, which can cause overlap issues in some configurations.

BaseAdapter is the abstract base class that you extend to create custom adapters for ListView and other AdapterView widgets. ListAdapter is an interface, not a class you extend. CustomAdapter is not a built-in Android class - it's a name you might give to your own implementation.

Android's security model prevents apps from changing network type (2G/3G/4G) programmatically without root access. The MODIFY_PHONE_STATE permission is only available to system apps or rooted devices. This restriction protects users from apps forcing them onto slower networks or bypassing user preferences.

Android's density-independent pixel ratios are: 3 (ldpi 0.75x), 4 (mdpi 1x baseline), 6 (hdpi 1.5x), 8 (xhdpi 2x), 12 (xxhdpi 3x), 16 (xxxhdpi 4x). These are the preferred scaling ratios for providing image assets. The 1:2:4:8 pattern is incorrect - Android uses 4:3 scaling increments, not powers of 2.

Android allows creating custom keyboards (Input Method Editors) without root access. You implement the InputMethodService and declare it in your manifest. The user must explicitly enable your keyboard in system settings, which is a security feature but doesn't require root.

Using Intent.ACTION_VIEW with a URI creates an Implicit Intent because you're specifying an action and data, but not the exact component to handle it. Android resolves the component at runtime based on the registered intent filters. Explicit intents specify the component class directly (new Intent(context, MyClass.class)).

Content Providers are the Android component designed specifically for sharing structured data between applications. Services run background operations, Intents enable messaging between components, and Activities display UI - none of these are primarily for data sharing across apps.

The UserDictionary content provider stores words that users have added to their personal dictionary (for autocorrect and suggestion purposes). It doesn't store device users, login credentials, or general language words from the system dictionary - only user-added custom words.

ContentResolver is the client-side class that applications use to communicate with Content Providers. You call getContentResolver() to get an instance, then use its query(), insert(), update(), and delete() methods. ContentProvider is the server-side class you implement to expose data.