使用NDK在Android Studio 1.0.2中生成.so文件

Question

我一直在努力获得一个非常简单的NDKSample应用程序,这个应用程序按照此处的步骤进行构建.我的问题是,我无法让Android Studio生成.so文件,因此我没有库.

我知道NDK支持现在已被弃用,并且今年早些时候会提供替代方案,但是目前似乎没有任何东西阻止我使用此功能.当我构建我的项目时,我收到以下警告(不是错误):

警告[Project :: app]不推荐使用当前的NDK支持.将来会提供替代方案.

我的项目构建,但是当我运行.apk它崩溃(如预期),因为它无法找到库/ .so文件.我们希望在构建项目时生成这些,根据示例,这是正确的吗？这是错误:

java.lang.UnsatisfiedLinkError:dalvik.system.PathClassLoader [DexPathList [[zip file"/data/app/com.example.ndksample-1/base.apk"],nativeLibraryDirectories=[/vendor/lib,/ system/lib] ]]找不到"libMyLib.so"

关于我的环境

Windows 7,Android Studio 1.0.2,ADB正在运行Nexus 5(模拟器-5554)

我的代码

根据例子:

主Activity.java

package com.example.ndksample;

//import android.support.v7.app.ActionBarActivity;
// This line is not needed as we are not targetting older devices
import android.app.Activity; //Import this app package to use onCreate etc.
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;


public class MainActivity extends Activity {

    static{
        System.loadLibrary("MyLib");
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView tv = (TextView) findViewById(R.id.my_textview);
        tv.setText(getStringFromNative());
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public native String getStringFromNative();
}

activity_main.xml中

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <TextView
        android:id="@+id/my_textview"
        android:text="@string/hello_world" android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</RelativeLayout>

main.c中

#include "com_example_ndksample_MainActivity.h"
/* Header for class com_example_ndksample_MainActivity */

JNIEXPORT jstring JNICALL Java_com_example_ndksample_app_MainActivity_getStringFromNative
    (JNIEnv * env, jobject obj)
    {
        return (*env)->NewStringUTF(env, "Hello from Kyle");
    }

build.gradle note:app

apply plugin: 'com.android.application'

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId "com.example.ndksample"
        minSdkVersion 15
        targetSdkVersion 21
        versionCode 1
        versionName "1.0"

        ndk {
            moduleName "MyLib"
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:21.0.3'
}

local.properties

## This file is automatically generated by Android Studio.
# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
#
# This file should *NOT* be checked into Version Control Systems,
# as it contains information specific to your local configuration.
#
# Location of the SDK. This is only used by Gradle.
# For customization when using a Version Control System, please read the
# header note.
sdk.dir=D\:\\Programs\\Android\\Android SDK
ndk.dir=D\:\\Programs\\Android\\Android NDK

如果有人能帮忙,我的问题是:

最终,我如何生成所需的.so文件!! ??

可能有助于回答主要问题的子问题:

我的目录布局在app下有我的jni目录(所以NDKSample/app/jni),这是正确的吗？我在这里建议不要将c文件放在标准的jni目录中.我试验了这个,在建造项目时,它崩溃了.错误:

*FAILURE:构建因异常而失败.

• 出了什么问题:任务执行失败':app:compileDebugNdk'.

  com.android.ide.common.internal.LoggedErrorException:无法运行命令:D:\ Programs\Android\Android NDK \ndk-build.cmd NDK_PROJECT_PATH = null APP_BUILD_SCRIPT = C:\ Users\Kyle\AndroidStudioProjects\NDKSample\app\build\intermediates \ndk\debug\Android.mk APP_PLATFORM = android-21 NDK_OUT = C:\ Users\Kyle\AndroidStudioProjects\NDKSample\app\build\intermediates \ndk\debug\obj NDK_LIBS_OUT = C:\ Users\Kyle\AndroidStudioProjects\NDKSample\app\build\intermediates \ndk\debug\lib APP_ABI = all错误代码:1*

上面的英特尔示例并没有指示我构建一个Android.mk文件,示例没有,他生成一个工作的应用程序.我试过把一个放在jni目录中,但它没有帮助.我应该创建一个,如果是的话,我应该把它放在哪里

我的目录的下图是否正确？

任何帮助将不胜感激.

凯尔

Answer 1

Android Studio中当前的NDK支持很少,因此他们将其弃用为1.0.

使用它时,会自动生成Android.mk文件,并在构建项目时编译源代码.现在似乎编译失败了,但您应该能够从Gradle控制台获取初始错误消息.

如果您没有收到任何其他错误消息,我怀疑对ndk-build的调用失败,因为NDK的安装路径中有一个空格(Android NDK)

您可以修复当前错误并继续当前设置,或禁用默认NDK集成,创建Android.mk/Application.mk文件并自行调用ndk-build(.cmd)或从任务中调用:

import org.apache.tools.ant.taskdefs.condition.Os

android {
    sourceSets.main {
        jniLibs.srcDir 'src/main/libs' //set .so files location to libs
        jni.srcDirs = [] //disable automatic ndk-build call
    }

    // call regular ndk-build(.cmd) script from app directory
    task ndkBuild(type: Exec) {
        if (Os.isFamily(Os.FAMILY_WINDOWS)) {
            commandLine 'ndk-build.cmd', '-C', file('src/main').absolutePath
        } else {
            commandLine 'ndk-build', '-C', file('src/main').absolutePath
        }
    }
    tasks.withType(JavaCompile) {
        compileTask -> compileTask.dependsOn ndkBuild
    }
}