JNI development under Android Studio (II) : C/C++ code writing and compilation
Today send two basic JNI development and configuration of the article, may everyone in many application layer development, but I feel the JNI base configuration and principle of development it is necessary to know something about, just push two very basic, everyone can understand, if you feel in less than now, you can see two eyes to know a little bit about the underlying process, It might help you in the future.
With the launch of Android Studio, more and more developers are migrating their projects from Eclipse to Android Studio, showing that Android Studio has a clear advantage over Eclipse. Also for JNI development, Android Studio is much easier to configure than Eclipse. This article introduces the JNI development configuration for Android Studio.
First, directly use the. So library
Unlike Eclipse, the.so library is placed under the jniLibs directory, as shown below:
It works the same way as in Eclipse, using System.loadLibrary("libName") to load libraries directly.
Second, use C/C++ source code
1. Download, install and configure the NDK
The first step is to download the NDK. You can download the NDK yourself, then unpack it, then specify the NDK directory, and configure the path of the NDK in the local.properties file, as shown in the following figure:
You can also set it up in Android Studio to download the corresponding version of the NDK. The steps are as follows:
● On the menu bar, go to "File"-"Settings" to open the Settings screen.
● Go to "Appearance Behavior"-"System Settings"-"Android SDK" and switch to the "SDK Tool" TAB;
● Then find the NDK tick;
● Click "Apply" button, and then click "OK" in the pop-up window, it will automatically download;
● Wait for the automatic download and installation to complete, click "Finish" to complete the installation.
As shown below:
The default NDK installation directory for Android Studio is the SDK directory. After the installation is complete, the NDK path Settings in the local.properties file will be automatically updated.
2. Add NDK modules to Gradle
Open the build.gradle file under app module and add NDK module under defaultConfig module, as shown in the figure below:
ModuleName is the name of the LOCAL_MODULE variable in the android. mk file in Eclipse development, which corresponds to the name of the.so loaded by system.loadLibrary (). For example, moduleName is set to "JniTest", so the file name is "libJniTest. So ", and the loading name is "system.loadLibrary ("JniTest");
AbiFilters specifies the platform to be allocated, or if not, all supported platforms will be compiled. Currently, seven supported platforms are armeabi, ArmeabI-V7A, ARM64-V8A, MIPS, MIPS64, x86, and X86_64.
LdLibs is the library to link to, which was originally specified by the LOCAL_LDLIBS variable in Android.mk.
3. Add C/C++ files
By default, C/C++ files are stored in the [module]/ SRC /main/jni/ directory, as shown below:
Of course, you can also modify the build.gradle configuration to specify other paths. In the "android.sourcesets. main" module, use "jni.srcDirs" to specify the path of jNI, as shown below:
This concludes the basic configuration of JNI development in Android Studio, and the next article will cover C/C++ coding and compilation in Android Studio.
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