Android C++ Example

5 min read Jun 28, 2024

Android C++ Example: A Simple "Hello World" App

This article will guide you through creating a basic Android application using C++ with the Android Native Development Kit (NDK). This example will display "Hello World" on the screen, demonstrating the fundamental process of developing Android apps with C++.

Prerequisites

Android Studio: Download and install the latest version of Android Studio from the official website.
Android NDK: Android Studio will prompt you to install the NDK during project setup. If not, you can download it separately from the official website.

Project Setup

Create a new project:
- Open Android Studio and select "Start a new Android Studio project."
- Choose "Empty Compose Activity" as the template.
- Name your project (e.g., "HelloWorldCpp").
- Select your minimum API level.
- Click "Finish".
Enable C++ Support:
- Go to "File" -> "Project Structure".
- Navigate to "Modules" -> YourProjectName (e.g., "HelloWorldCpp").
- Click on "Properties" in the right pane.
- Check the box for "C/C++ Support".
- Click "OK" to save changes.

Code Implementation

Create a C++ Native Code File:
- Inside the cpp directory of your project, create a new file named native-lib.cpp.
- Add the following C++ code to native-lib.cpp:
```
#include 
#include 

extern "C" JNIEXPORT jstring JNICALL
Java_com_example_helloworldcpp_MainActivity_stringFromJNI(
        JNIEnv *env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
}
```
Explanation:
- This code defines a function stringFromJNI that is called from your Java code.
- JNIEXPORT and JNICALL are macros required for JNI (Java Native Interface) functions.
- jstring is the JNI data type representing a Java string.
- The function returns a string "Hello from C++" back to the Java code.
Modify Java Code:
- Open the MainActivity.kt file.
- Add the following code inside the onCreate method:
```
// ... existing code ...

// Load the native library
System.loadLibrary("native-lib")

// Access the native function
val text = stringFromJNI()

// Set the text view
binding.sampleText.text = text

// ... rest of the code ...
```
Explanation:
- System.loadLibrary("native-lib") loads the native library we created (native-lib.cpp).
- stringFromJNI() calls the native C++ function defined in native-lib.cpp.
- The returned value is stored in the text variable.
- Finally, the text is set to the sampleText TextView.

Build and Run

Build the project: Click the "Run" button (green play icon) in Android Studio.
Deploy the app: Select a device or emulator to run the app.
View the result: Once the app launches, you should see "Hello from C++" displayed on the screen.

Conclusion

This simple example demonstrates how to use C++ code in your Android applications using the NDK. You can build upon this basic structure to create more complex and feature-rich Android apps using the power of C++. Remember to learn more about JNI, NDK, and C++ concepts to develop robust and efficient Android apps.

Android C++ Example