Resource res files and how to change app name and icon

1. res Directory Structure

The res/ directory is organized into subdirectories by resource type:

Directory	Purpose
`drawable`	General images (e.g., backgrounds, illustrations)
`mipmap`-prefixed	App icons (Launcher Icons)
`values`	Strings, styles, colors, etc.
`layout`	Layout files

2. Why Are There So Many mipmap and drawable Folders?

To support various screen densities, Android provides multiple directories:

drawable-hdpi      → High density
drawable-xhdpi     → Extra-high density
drawable-xxhdpi    → Extra-extra-high density
drawable-xxxhdpi   → Highest density

The same applies to mipmap, with folders like mipmap-hdpi, mipmap-xhdpi, mipmap-xxhdpi, etc.

How it works: Prepare different resolutions of the same image and place them in the corresponding folders. At runtime, the system automatically selects and loads the most suitable set based on the device’s screen density.

3. How to Reference Resources

3.1 String Resources

Defined in res/values/strings.xml:

<resources>
    <string name="app_name">My Application</string>
</resources>Code language: HTML, XML (xml)

References are used differently depending on the context:

Context	Reference Format	Example
In XML files	`@string/app_name`	`android:text="@string/app_name"`
In Java code	`R.string.app_name`	`getString(R.string.app_name)`

3.2 Referencing Images and Icons

Note: You cannot use Java syntax like R.mipmap.xxx directly in XML!

Resource Type	In XML	In Java Code
Icon (mipmap)	`@mipmap/ic_launcher`	`R.mipmap.ic_launcher`
Image (drawable)	`@drawable/bg_image`	`R.drawable.bg_image`
Layout	—	`R.layout.activity_main`
String	`@string/app_name`	`R.string.app_name`

Side-by-side example:

<!-- In XML: use @ prefix -->
android:icon="@mipmap/school"Code language: HTML, XML (xml)

// In Java: use R. prefix
setContentView(R.layout.activity_main);Code language: JavaScript (javascript)

4. Resource References in AndroidManifest.xml

Open AndroidManifest.xml. Inside the application tag, you’ll already see several resource references:

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">Code language: HTML, XML (xml)

Attribute	Referenced Resource	Purpose
`android:icon`	`@mipmap/ic_launcher`	App icon
`android:label`	`@string/app_name`	App name
`android:roundIcon`	`@mipmap/ic_launcher_round`	Round app icon
`android:theme`	`@style/AppTheme`	App theme

5. Hands-on Exercise: Change App Name and Icon

Step 1: Change the App Name

Open res/values/strings.xml:

<resources>
    <string name="app_name">FoxDevelop</string>
</resources>Code language: HTML, XML (xml)

After saving, the app name on your device’s home screen will become “FoxDevelop”.

Step 2: Prepare the Icon File

Download a PNG icon

File naming rules: Do not use hyphens -; only use underscores _, lowercase letters, or numbers
- ✅ school_bell.png
- ❌ school-bell.png

Step 3: Place in the Correct Directory

Copy the icon file into res/mipmap-xxhdpi/ (or the corresponding mipmap folder for your target resolution).

Step 4: Modify AndroidManifest.xml

<application
    android:icon="@mipmap/school_bell"
    android:roundIcon="@mipmap/school_bell"
    ... >Code language: HTML, XML (xml)

Step 5: Run Again

Click the ▶ Run button to deploy to the emulator. You should see:

The app name on the home screen changes to “FoxDevelop”
The app icon becomes the school_bell.png you set

6. Summary

Key Point	Description
Resource reference rule	XML uses `@type/name`, Java uses `R.type.name`
Multi-resolution adaptation	Place images for different resolutions in separate folders; the system picks automatically
Change app name	Modify `app_name` in `res/values/strings.xml`
Change app icon	Replace the PNG in the `mipmap` folder and update `android:icon` in `AndroidManifest.xml`
File naming convention	Only lowercase letters, numbers, and underscores; no hyphens

Remember this in one sentence: XML uses @, Java uses R.; icons go in mipmap, images in drawable, strings in values.