javah -d jni -classpath /platforms/android-23/android.jar:/extras/android/support/v7/appcompat/libs/android-support-v7-appcompat.jar:/extras/android/support/v7/appcompat/libs/android-support-v4.jar././build/intermediates/classes/debug. (Windows users replace forward slashes(/) with back slashes (\) and colon separators (:) with semi colons( )). Next, invoke javah using the following command (Replace and to match your own path). Using the terminal window at the bottom of the screen, move into the src/main/ directory using the cd command cd src/main We fix this by first generating the appropriate C/C++ header files using the C Header and Stub File Generator - javah. This will compile and generate some necessary class files.Īndroid studio will mark this as an error because we don't have the corresponding JNI method defined yet. Save and build your project by selecting Build > Make Project public static native String getStringFromNative() This is an abstract method with the native keyword. To begin, add a native method to your class file. ![]() ![]() In order to invoke native C/C++ code in your application, you have to use the Java Native Interface (JNI). In the SDK tools tab, scroll down the bottom of the page and select Android NDK and then click apply to install. Or from the tools menu Tools > Android > SDK Manager You can access this through File > Settings > Appearance & Behavior > System Settings > Android SDK` Now that you have a new project, you need to download the NDK using the SDK manager built into Android studio. ![]() Now just select the defaults for everything else, by hitting Next until the project is created. As well as the Different form factors- Android Wear, TV and Auto. Next you have to select a minimum SDK or Android version which your application will support. Select an application name and company name (this will be used as the package name, so you company domain name should be used). This is done by selecting Start a new Android Studio project in the Quick Start menu when you first launch android studio. I'll also be using the older deprecated NDK plugin rather than the new experimental version. This tutorial was put together using Android Studio 1.4.1 with the most recent API version 23. Getting the NDK up and running on the other hand can be a pain. It's easier to just mmap a file and use that instead, which is too bad since a basic file mapping isn't nearly as mobile-friendly as ashmem.Android allows you to compile and execute native code written in C/C++ for increased computational performance. It's a lot of work for such a simple feature, I know. Instead, you'd need to pass the handle via a binder service implemented in Java. All it takes is somebody deciding that "mFD" is too vague and "mFileDescriptor" would be a better name, or some such.) If you want to play with fire, I'd suggest retrieving the descriptor by type rather than by name, since the type is very unlikely to change.Ĭedric also proposes implementing a Binder in C++, but this puts you back where you started because Binder is also not included in the NDK. Cedric Fung proposes using reflection to retrieve the ashmem handle by name, which will work but may break in future frameworks. Unfortunately, if you're using shared memory to boost performance, multiple round trips through JNI aren't an attractive proposition. The Java class wraps ashmem and provides read/write methods to access it. As with so many things in Android, the answer is to use JNI.
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