Android

Information

Are you ready to step into the heart of a global Android revolution, where millions of users and developers collaborate to improve the open source mobile operating system, giving you endless possibilities to customize your device and operating system. Unleash your creativity and make your smartphone, tablet, or smartwatch truly your own with the endless array of apps and features available on Android, tailored to fit your unique needs and preferences. Our job at KBVE will be to provide you with everything you need to deploy your own Android application on almost any device!

This one page guide is meant to serve as your resource manual moving forward, we will start with the cheat sheet below, that makes it easy to reference back in the future.

Cheatsheet

The ADB cheat sheet is an essential resource for navigating and managing Android operating systems and applications via the Android Debug Bridge (ADB). It offers a comprehensive list of basic commands that facilitate various tasks such as installing apps, debugging issues, and accessing device logs. While the cheat sheet covers a wide range of functionalities, it’s important to note that some commands require root access, and certain Android versions may necessitate specific tweaks to the standard commands. This makes the cheat sheet a versatile and indispensable tool for both novice users and experienced developers working with Android devices.

Device Commands

Android ADB Device commands are commands that you can use to control the Android device over USB from a computer. You can use them to list all devices, restart the ADB server, and reboot connected devices.

Command	Description	Notes / Variants
adb devices	List all connected devices.
adb devices -l	Query additional information (model, product, transport ID).	Useful for identifying multiple devices.
adb get-state	Display the current device state (device, offline, or unauthorized).
adb get-serialno	Query the device’s serial number.
adb root	Launch the ADB daemon (adbd) with root permissions.	May fail on production builds: adbd cannot run as root in production builds.
adb start-server	Start the ADB server daemon.	Runs automatically if missing when using other ADB commands.
adb kill-server	Terminate the ADB server process.	Use to restart ADB cleanly if it becomes unresponsive.
adb reboot	Reboot the currently connected device.	Accepts optional args like bootloader or recovery.
adb help	Display general help and usage information.	Lists all supported subcommands.

Shell

Danger

Warning: Shell commands can brick your operating system, so make sure to double check them before running.

ADB shell is a command-line interface that you can use to access the shell and run various commands on your Android device. You can use ADB shell commands to perform actions such as changing the resolution of your device display, uninstalling bloatware or system apps, enabling and disabling features, modifying the system files, ect..

Note

Remember to keep a backup of the commands that you run via shell, I recommend creating a log.txt file and output all the commands to that file.

Command	Description	Notes / Variants
adb shell	Launch the interactive shell terminal on the connected device.	Equivalent to opening a remote terminal session.
adb -s $deviceString $deviceCommand	Send a command ($deviceCommand) to a specific device identified by $deviceString.	Useful when multiple devices are connected.
adb shell pwd	Print the current working directory on the device.
adb shell ls	List the contents of the current directory.
adb shell ls -s	List directory contents with file size information.
adb shell ls -R	Recursively list contents of all subdirectories.
adb shell netstat	Display current TCP/IP network connections.	Useful for debugging sockets and ports.
adb shell dumpsys	Dump system service information and status reports.	A powerful diagnostic tool for system introspection.
adb shell dumpsys iphonesybinfo	Retrieve IMEI and related telephony information.	Typo in some Android versions — should be iphonesubinfo.
adb shell dumpsys battery	Display current battery status and related data.
adb shell dumpsys battery set level $v	Manually set battery level from 0 to 100.	Useful for testing low-power states.
adb shell dumpsys battery reset	Reset battery state to default (real readings).
adb shell dumpsys activity $package	Dump activity information for a specific package.
adb shell pm list features	List available hardware and software features.
adb shell service list	List all registered Android system services.	Often used before running targeted dumpsys queries.
adb shell wm	Base command for WindowManager operations.	Placeholder — requires subcommands.
adb shell wm size	Show the current screen resolution.
adb shell wm size $WxH	Set custom screen resolution (e.g., 1080x1920).
adb shell wm size reset	Reset screen resolution to default.
adb shell wm density	Show the current display density (DPI).
adb shell wm density reset	Reset display density to system default.
adb shell ps	List all running processes on the device.	Similar to Linux ps command.
exit	Exit the current ADB shell session.	Returns to the host terminal.

Key Events

Android Key Events - A quick breakdown for each event and how the operating system handles them.

Generic Android Keyevents:

  adb shell input keyevent

Keycode	Command Example	Description
0	adb shell input keyevent 0	Keycode 0
1	adb shell input keyevent 1	Soft Left
2	adb shell input keyevent 2	Soft Right
3	adb shell input keyevent 3	Home Button Event
4	adb shell input keyevent 4	Back Button Event
5	adb shell input keyevent 5	Call Event
6	adb shell input keyevent 6	End Call / Hangup Event
7	adb shell input keyevent 7	Keycode 0
8	adb shell input keyevent 8	Keycode 1 — Number 1
9	adb shell input keyevent 9	Keycode 2 — Number 2
10	adb shell input keyevent 10	Keycode 3 — Number 3
11	adb shell input keyevent 11	Keycode 4 — Number 4
12	adb shell input keyevent 12	Keycode 5 — Number 5
13	adb shell input keyevent 13	Keycode 6 — Number 6
14	adb shell input keyevent 14	Keycode 7 — Number 7
15	adb shell input keyevent 15	Keycode 8 — Number 8
16	adb shell input keyevent 16	Keycode 9 — Number 9
17	adb shell input keyevent 17	STAR (*) Key
18	adb shell input keyevent 18	Pound (#) Key

• Koltin: open class KeyEvent: InputEvent, Parcelable

• Java: public class KeyEvent extends InputEvent implements Parcelable

Note

The ADB cheatsheet provides a general list of basic commands for Android operating system and applications. Please note that certain commands require the device to be rooted, furthermore certain Android versions may require a tweak to the commands.

---

Android Data Storage

In Android, there are several ways to store data persistently. The choice of storage mechanism depends on the nature of the data and the requirements of the app. Below are the primary methods for data storage in Android:

Comparison of Storage Options

Storage Method	Visibility	Persistence	Complexity	Best For
SharedPreferences	Private	Until app uninstall	Low	Small key-value pairs
Internal Storage	Private	Until app uninstall	Low	Private files
External Storage	Public	Until manually deleted	Medium	Large/shared files
SQLite Database	Private	Until app uninstall	High	Structured data
Room	Private	Until app uninstall	Medium-High	Structured data with compile-time safety

When choosing a storage method, consider the type of data you’re storing, how much data you need to store, the required level of security, and the complexity you’re willing to manage in your app.

1. SharedPreferences

SharedPreferences is a framework that allows you to save and retrieve key-value pairs of primitive data types.

Use Cases

• Storing user preferences.
• Saving settings or configuration data.

Advantages:

• Simple to use for small amounts of data
• Data persists across app restarts

Disadvantages:

• Not suitable for large or complex data structures
• Not encrypted by default

Java Code Example

// Saving data to SharedPreferences
SharedPreferences sharedPref = getSharedPreferences("MyPrefs", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString("key_name", "value");
editor.apply();

// Retrieving data from SharedPreferences
SharedPreferences sharedPref = getSharedPreferences("MyPrefs", Context.MODE_PRIVATE);
String value = sharedPref.getString("key_name", "default_value");

2. Internal Storage

Internal Storage is used to store private data within the device’s internal memory.

Use Cases

• Storing sensitive data.
• Files that should not be accessible to other apps.

Advantages:

• Data is private to the app.
• Files are removed when the app is uninstalled.

Disadvantages:

• Limited by device storage.
• Not easily accessible for backup.

Java Code Example

// Writing to internal storage
String filename = "myfile";
String fileContents = "Hello, World!";
FileOutputStream fos = openFileOutput(filename, Context.MODE_PRIVATE);
fos.write(fileContents.getBytes());
fos.close();

// Reading from internal storage
FileInputStream fis = openFileInput(filename);
InputStreamReader isr = new InputStreamReader(fis);
BufferedReader br = new BufferedReader(isr);
StringBuilder sb = new StringBuilder();
String line;
while ((line = br.readLine()) != null) {
    sb.append(line);
}
String fileContents = sb.toString();
fis.close();

3. External Storage

External Storage is used to store public data on the shared external storage. It’s typically used for storing larger files.

Use Cases

• Storing media files (images, videos, audio)
• Documents that need to be shared with other apps.

Advantages:

• Larger storage capacity
• Files can be shared with other apps

Disadvantages:

• Not secure, as other apps can access the files
• Files may remain after app uninstallation

Permissions

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

Java Code Example

// Writing to external storage
String filename = "myfile";
String fileContents = "Hello, World!";
File file = new File(getExternalFilesDir(null), filename);
FileOutputStream fos = new FileOutputStream(file);
fos.write(fileContents.getBytes());
fos.close();

// Reading from external storage
File file = new File(getExternalFilesDir(null), filename);
FileInputStream fis = new FileInputStream(file);
InputStreamReader isr = new InputStreamReader(fis);
BufferedReader br = new BufferedReader(isr);
StringBuilder sb = new StringBuilder();
String line;
while ((line = br.readLine()) != null) {
    sb.append(line);
}
String fileContents = sb.toString();
fis.close();

4. SQLite Database

SQLite is a lightweight relational database embedded within Android.

Use Cases

• Structured data storage.
• Complex querying requirements.
• Managing complex data relationships

Advantages:

• Efficient for complex queries and large datasets
• Supports transactions and data integrity

Disadvantages:

• More complex to set up and use compared to other options
• Overkill for simple data storage needs

Java Code Example

// Creating a database helper
public class MyDatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "mydatabase.db";
    private static final int DATABASE_VERSION = 1;

    public MyDatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE mytable (id INTEGER PRIMARY KEY, name TEXT)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS mytable");
        onCreate(db);
    }
}

// Using the database helper
MyDatabaseHelper dbHelper = new MyDatabaseHelper(context);
SQLiteDatabase db = dbHelper.getWritableDatabase();

// Inserting data
ContentValues values = new ContentValues();
values.put("name", "John Doe");
long newRowId = db.insert("mytable", null, values);

// Querying data
Cursor cursor = db.query("mytable", new String[]{"id", "name"}, null, null, null, null, null);
while (cursor.moveToNext()) {
    long itemId = cursor.getLong(cursor.getColumnIndexOrThrow("id"));
    String itemName = cursor.getString(cursor.getColumnIndexOrThrow("name"));
}
cursor.close();
db.close();

5. Room Database

Room is an abstraction layer over SQLite that provides a more robust database access while harnessing the full power of SQLite.

Use Cases:

• When you need a robust database solution but want to avoid the complexity of raw SQLite

Advantages:

• Compile-time verification of SQL queries
• Convenient annotations to define database structure
• Easy integration with other Architecture components

Disadvantages:

• Adds additional dependencies to your project
• May be overkill for very simple data storage needs

Java Code Example

// Define Entity
@Entity(tableName = "user")
public class User {
    @PrimaryKey
    public int id;
    public String name;
}

// Define DAO
@Dao
public interface UserDao {
    @Insert
    void insert(User user);

    @Query("SELECT * FROM user WHERE id = :id")
    User getUserById(int id);
}

// Define Database
@Database(entities = {User.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
    public abstract UserDao userDao();
}

// Using Room
AppDatabase db = Room.databaseBuilder(getApplicationContext(),
        AppDatabase.class, "mydatabase").build();
UserDao userDao = db.userDao();

// Inserting data
User user = new User();
user.id = 1;
user.name = "John Doe";
userDao.insert(user);

// Querying data
User user = userDao.getUserById(1);

6. Content Providers

Content Providers manage access to a structured set of data. They encapsulate the data and provide mechanisms for defining data security.

Use Cases

• Sharing data between different applications.
• Accessing data from other applications.

Java Code Example

// Querying a content provider
Cursor cursor = getContentResolver().query(
        ContactsContract.Contacts.CONTENT_URI,
        null,
        null,
        null,
        null);

while (cursor.moveToNext()) {
    String id = cursor.getString(
            cursor.getColumnIndex(ContactsContract.Contacts._ID));
    String name = cursor.getString(
            cursor.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME));
}
cursor.close();

---

React Native

This part of the guide goes into the specific parts of React Native and Android, we do try to keep all our react native notes into one area. We recommend going to the rn section as well, but there might be double notes in this section.