Comprehensive Guide to Accessing and Using Android Default Icons

Overview of Android System Icon Resources

In Android application development, developers frequently need to utilize default icon resources provided by the system. These icons adhere to Android design guidelines, ensuring interface consistency and professionalism. However, developers often encounter "resource not public" error messages when referencing these resources, primarily due to insufficient understanding of the system resource access mechanism.

Analysis of System Resource Directory Structure

The Android SDK provides complete system resource files, including various default icons. These resource files are located in specific paths within the Android SDK installation directory:

\path-to-your-android-sdk-folder\platforms\android-xx\data\res

Here, android-xx represents the specific Android API level, such as android-33 for Android 13. This directory contains all system resource files, organized by type in subdirectories like drawable, layout, and values.

Accessing Icons Through R.drawable Constants

A more recommended approach is to use the R.drawable constant class provided by Android. This method offers better type safety and IDE support:

android.R.drawable.ic_menu_refresh
android.R.drawable.ic_menu_compose
android.R.drawable.ic_menu_save

When using this approach in code, developers can utilize IDE auto-completion to view all available icon constants. This method avoids compatibility issues that may arise from directly referencing resource IDs.

Resolving Non-Public Resource Errors

The error in the original question stemmed from using incorrect resource referencing methods:

<item
    android:id="@+id/preference"
    android:icon="@android:drawable/ic_menu_refresh"
    android:showAsAction="ifRoom" />

The correct referencing approach should be:

<item
    android:id="@+id/preference"
    android:icon="@android:drawable/ic_menu_refresh"
    android:showAsAction="ifRoom" />

Alternatively, setting the icon programmatically:

menuItem.setIcon(android.R.drawable.ic_menu_refresh);

Material Design Icon Resources

With the evolution of Android design language, Material Design has become the new standard. Developers can obtain the latest icon sets from the official design resources website:

Google provides a comprehensive Material Design icon library containing various styles and sizes of icon resources. These icons follow modern design principles and support multiple color themes and state changes.

Best Practice Recommendations

In practical development, it is recommended to prioritize using android.R.drawable constants for referencing system icons, as this approach offers better maintainability and compatibility. For custom icons, consider using resources from the Material Design icon library to ensure modern appearance and consistency in the application interface.

It is important to note that system icons may vary across different Android versions, so version compatibility should be considered when referencing. Conditional resource selection or runtime checks can be employed to ensure consistent display across different devices.