如何将JNI(C/C ++本机代码)添加到现有的Android Studio项目 [英] How to add JNI (C/C++ native code) to existing Android Studio project

问题描述

就像标题中所说的那样-如何在不破坏当前项目(包括gradle和proguard设置)的情况下将本机代码添加到现有的Android Studio项目中?

Like the title says - how to add native code to existing Android Studio project, without breaking the current project, including gradle and proguard settings?

推荐答案

从您现有的项目中遵循以下步骤:

Follow this steps from your existing project:

    apply plugin: 'com.android.model.application'

    model {
        android.signingConfigs {
            create ("myConfig") {
                keyAlias '--your-key-alias--'
                keyPassword '--key-password--'
                storeFile file('--/path/to/keystore.jks--')
                storePassword '--store-password--'
            }
        }
        android {
            compileSdkVersion 25
            buildToolsVersion '25.0.2'

            defaultConfig {
                applicationId "--your.app.name--"
                minSdkVersion.apiLevel 19
                targetSdkVersion.apiLevel 25
                versionCode 1
                versionName "1.0"
            }
            buildTypes {
                release {
                    minifyEnabled true
                    proguardFiles.add(file('proguard-android-optimize.txt'))
                    proguardFiles.add(file('proguard-rules.pro'))
                    signingConfig = $("android.signingConfigs.myConfig")
                }
            }
            ndk {
                moduleName "--c-file--"
                ldLibs.addAll(["android", "log"])
            }

        }
        android.dexOptions {
            javaMaxHeapSize "2048m"
        }
    }

    dependencies {
        compile fileTree(dir: 'libs', include: ['*.jar'])
        testCompile 'junit:junit:4.12'
        compile 'com.android.support:appcompat-v7:25.3.1'
    }

您可以复制/粘贴上面的代码，并至少使用"--value--"修改值.匹配您的.

You can copy/paste the above code and modify at least the values with "--value--" to match yours.

它说像这样:

dependencies {
    classpath 'com.android.tools.build:gradle:2.3.3'
}

对此:

dependencies {
    classpath 'com.android.tools.build:gradle-experimental:0.9.3'
}

我的示例中的数字 0.9.3 是gradle-experimental的最新版本， .如果尚未，请最终将 gradle-wrapper.properties 中的gradle版本更改为Android Studio推荐的版本.

The number in my example 0.9.3 is the latest version of gradle-experimental to be found here. Eventually change your gradle version in gradle-wrapper.properties to the version recommended by Android Studio if you did not already.

proguard-android-optimize.txt至app/proguard-android-optimize.txt

像这样

static {
    System.loadLibrary("--c-file--");
}
private native byte my_jni(Context context, byte[] mByte, int i);

改变您的需求.上面的示例加载c文件(不带扩展名将其写入)-在gradle文件中声明的文件相同，并调用函数my_jni，传递应用程序的Context，一些字节数组和一些int，期望这些函数返回一个字节.

changing to your needs. The example above loads the c-file (write it without the extension) - the same one declared in the gradle file, and calls the function my_jni, passing the application's Context, some byte array and some int, expecting that the functions returns a byte.

现在，函数的名称以红色突出显示-单击行上的红色指示灯，允许Android Studio创建它Create function ....这样会在您的c文件中创建函数，并将焦点更改为它.

Now the name of your function is highlighted in red - allow Android Studio to create it Create function ... with clicking on the red lamp on the row. This creates the function in your c file and changes focus to it.

进一步阅读提示:

• 注意free所有malloc的内容，对于每个GetByteArrayElements的ReleaseByteArrayElements，依此类推

• Take care to free everything you malloc, ReleaseByteArrayElements for every GetByteArrayElements and so on

请注意如何正确地将C中的某些危险值返回给Java，例如数组和字符串

Take care how to properly return some dangerous values from C to Java, like arrays and Strings

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