Android Studio 2.2 Jni 調試

Jni是android提供的與其他語言交互的接口，常用的就是c或c++，之前寫jni代碼是非常痛苦的，一方面像寫記事本一樣沒有各種函數提示，一方面無法調試，單靠打log效率非常低，所以之前都有點不想寫jni的代碼，但是最近得知了jni可以像Java一樣動態調試，非常感興趣，經過一番折騰，把具體步驟介紹一下。

 

1、環境：

   Android studio 2.2以上

   Jdk 1.8以上

   NDK r12+

   安裝CMake、LLDB

2、新建工程，將Include C++ Support勾上

 

 

 

 

 

 

 

3、C++ Standard選默認的就行，下面第一個“Exception Support”代表處理c++異常，最好勾上，點擊Finish

 

 

4、目錄主要變化，因爲採用CMake,所以默認C代碼放在cpp目錄下，然後比較重要的一個文件是CMakeLists.txt

 

 

 

5、CMakeLists介紹，如下是CMakeLists文件的內容：

 

#Sets the minimum version of CMake required to build the native
# library. You should either keep the default value or only pass a
# value of 3.4.0 or lower.

cmake_minimum_required(VERSION 3.4.1)

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds it for you.
# Gradle automatically packages shared libraries with your APK.
include_directories( imported-lib/include/ )
add_library( # Sets the name of the library.
             native-lib2

             # Sets the library as ashared library.
             SHARED

             # Provides a relative pathto your source file(s).
             # Associated headers in thesame location as their source
             # file are automaticallyincluded.
             src/main/cpp/native-lib.cpp)

add_library(tmms-au SHARED src/main/cpp/tmms-au-jni.c)
add_library(tmloader STATIC IMPORTED)
set_target_properties( # Specifies the target library.
                       tmloader

                       # Specifies theparameter you want to define.
                       PROPERTIESIMPORTED_LOCATION

                       # Provides thepath to the library you want to import.
                      src/main/cpp/libtmloader.a )

# Searches for a specified prebuilt library and stores the path as a
# variable. Because system libraries are included in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
              log-lib

              # Specifies the name of theNDK library that
              # you want CMake to locate.
              log )

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in the
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries(tmms-au tmloader ${log-lib})
target_link_libraries( # Specifies the target library.
                       native-lib2

                       # Links the targetlibrary to the log library
                       # included in theNDK.
                       ${log-lib} )

說明：

1、 include_directories( imported-lib/include/ )作用就是將所有頭文件放在一個目錄裏，然後指定目錄位置，以後在c代碼中include就不需要加路徑了。

2、 add_library(native-lib SHARED src/main/cpp/native-lib.cpp)該函數負責生成so文件相關信息，第一個參數是so文件名稱，第二個是類型，比如SHARED就是動態鏈接庫；第三個就是c文件所在路徑，注意頭文件可以直接在c代碼中包含路徑就行，可以不用在這邊寫。另外這個方法也可以用來導入其他的so文件，例如add_library(native-lib SHARED IMPORTED)，但是調用這個後一定要通過set_target_properties設置可執行文件的位置。

3、 find_library（log-lib log）是尋找NDK本地so文件,第一個參數是保存要找的so文件的路徑變量名，下面會用到，第二個參數就是要找的NDK中的so文件名。

4、 target_link_libraries（native-lib imported-lib ... ${log-lib}）作用是將其他的庫導入到你的目標so中，第一個參數就是目標so文件，後面的都是要導入的其他庫。

5、 接下來就能按照上面的步驟創建多個屬於自己的so文件了

6、build.gradle介紹：

applyplugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "24.0.1"
    defaultConfig {
        applicationId "com.example.myapplication"
        minSdkVersion 17
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags "-fexceptions"
            }
        }
        ndk {
            // Specifies the ABIconfigurations of your native
            // libraries Gradle shouldbuild and package with your APK.
            abiFilters  'armeabi'
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFilesgetDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
   /* externalNativeBuild {

        // Encapsulates your CMake buildconfigurations.
        cmake {

            // Provides a relative pathto your CMake build script.
            path"CMakeLists.txt"
        }
    }*/
    externalNativeBuild {
        ndkBuild {
            path "src/main/jni/Android.mk"
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include:['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2',{
        exclude group: 'com.android.support',module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.0.0'
    testCompile 'junit:junit:4.12'
}
 

1） defaultConfig.externalNativeBuild,裏面就是之前創建項目指定的一些選項，另外defaultConfig.ndk負責指定需要創建哪些類型的so文件，最好指定一下，不然會全部創建，非常慢的。

2) externalNativeBuild{
        // Encapsulates your CMake buildconfigurations.
        cmake {
            // Provides a relative pathto your CMake build script.
            path"CMakeLists.txt"
        }
這個負責指定CMakeLists.txt文件路徑。另外如果想要採用NDK來編譯，就要改成externalNativeBuild {
        ndkBuild {
            path "src/main/jni/Android.mk"
        }
  }

7、開始調試

按照上面所有步驟配置好後就能開始調試了，比較麻煩的一點是每次修改CMakeLists.txt最好要clean project一下，不然會出現很多沒必要的問題，這種方式和之前gradle-experimental創建的jni調試效果差不多，就是比較方便，不用修改插件了。好了，可以盡情的調試你的c代碼了！