三、构建和调试NDK应用

Create the project. Start a command-line console and enter the following command:

```cpp$ android create project \--target android-15 \--name HelloNDK \--path ~/Desktop/book-code/chapter3/HelloNDK \--activity HelloNDKActivity \--package cookbook.chapter3

```

类型

android工具可以在 Android SDK 文件夹的tools/目录下找到。如果你已经按照第 1 章、你好 NDK 设置了 SDK 和 NDK 开发，并且PATH配置正确，你可以直接从命令行执行android命令。否则，您需要输入android程序的相对路径或完整路径。这也适用于书中使用的其他 SDK 和 NDK 工具。

以下是 命令输出的截图:

转到HelloNDK项目文件夹，使用以下命令创建一个名为jni的文件夹:

```cpp$ cd ~/Desktop/book-code/chapter3/HelloNDK$ mkdir jni

```

在jni文件夹下 创建一个名为hello.c的文件，并添加以下内容:

```cpp

jstring Java_cookbook_chapter3_HelloNDKActivity_naGetHelloNDKStr(JNIEnv pEnv, jobject pObj){ return (pEnv)->NewStringUTF(pEnv, "Hello NDK!");}```

在jni文件夹下创建一个名为Android.mk的文件，内容如下:

cppLOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE := helloLOCAL_SRC_FILES := hello.cinclude $(BUILD_SHARED_LIBRARY)

使用以下命令构建本机库:

```cpp$ ndk-build

```

将HelloNDKActivity.java文件 修改为以下内容:

cpppackage cookbook.chapter3;import android.app.Activity;import android.os.Bundle;import android.widget.TextView;public class HelloNDKActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); TextView tv = new TextView(this); tv.setTextSize(30); tv.setText(naGetHelloNDKStr()); this.setContentView(tv); } public native String naGetHelloNDKStr(); static { System.loadLibrary("hello"); }}

Update the project. We have added a native library, so we need to update the project with the following command. Note that this command is only needed once unless we change the project settings, while the previous ndk-build command needs to be executed every time we update the native code:

```cpp$ android update project --target android-15 --name HelloNDK \--path ~/Desktop/book-code/chapter3/HelloNDK

```

以下是命令输出的屏幕截图:

Go to the project root folder, and build our project in the debug mode using the following command:

```cpp$ ant debug

```

在下面的截图中，我们显示了输出的最后几行，这表明成功的构建是:

输出apk将在bin/HelloNDK-debug.apk产生。

Create an emulator using the following command:

```cpp$ android --verbose create avd --name android_4_0_3 \--target android-15 --sdcard 32M

```

以下是 命令输出的截图:

Start the emulator, using the following command:

```cpp$ emulator -wipe-data -avd android_4_0_3

```

或者，我们可以使用命令“android avd”启动安卓虚拟设备管理器窗口，然后选择一个仿真器启动，如下所示:

Install the app on the emulator. We first check the device serial number by using the following command:

```cpp$ adb devices

```

以下是 命令输出的截图:

We then install the debug.apk file to the emulator by using the following command:

```cpp$ adb -s emulator-5554 install bin/HelloNDK-debug.apk

```

类型

如果只有一台设备连接到计算机，则无需指定设备序列号。在前面的命令中，我们可以删除“- s emulator-5554”。

Start the HelloNDK app on the emulator using the command in the following format:

```cpp$ adb shell am start -n com.package.name/com.package.name.ActivityName

```

在我们的示例中，我们使用以下命令:

```cpp$ adb -s emulator-5554 shell am start -n cookbook.chapter3/cookbook.chapter3.HelloNDKActivity

```

Run the app on a device.

假设设备序列号为HT21HTD09025，那么我们可以使用以下命令在 安卓设备上安装该应用。

```cpp$ adb -s HT21HTD09025 install bin/HelloNDK-debug.apk

```

在我们的示例中，我们使用以下命令启动应用:

```cpp$ adb -s HT21HTD09025 shell am start -n cookbook.chapter3/cookbook.chapter3.HelloNDKActivity

```

创建发布包。

Create a keystore. An Android app must be signed using a key from a keystore. A keystore is a collection of private keys. We can use the following command to create a keystore with a private key:

```cpp$ keytool -genkey -v -keystore release_key.keystore \-alias androidkey \-keyalg RSA -keysize 2048 -validity 10000 \-dname "CN=MyCompany, OU=MyAndroidDev, O=MyOrg, L=Singapore, S=Singapore, C=65" \-storepass testkspw -keypass testkpw

```

以下是命令输出的屏幕截图:

如图所示，创建了一个密码为testkwpw的密钥库，并将密码为testkpw的 RSA 密钥对添加到密钥库中。

键入命令“ant release”为应用构建一个apk。输出可以在 b i n 文件夹中找到作为HelloNDK-release-unsigned.apk。

Sign the apk by using the following command:

```cpp$ jarsigner -verbose -keystore -storepass -keypass -signedjar

```

对于我们的示例应用，命令 和输出如下:

Zip-align the apk file. The zipalign tool aligns the data inside an apk file for performance optimization. The following command can be used to align a signed apk:

```cpp$ zipalign -v 4

```

对于我们的示例应用，命令和输出如下:

Right-click on the project HelloNDKEclipse, select Android Tools | Add Native Support. A window similar to the following screenshot will appear. Click on Finish to dismiss it:

这将添加一个里面有两个文件(HelloNDKEclipse.cpp和Android.mk)的jni文件夹，并将 Eclipse 切换到 C/C++透视图。

在HelloNDKEclipse.cpp中增加以下 内容:

```cpp

jstring getString(JNIEnv* env) { return env->NewStringUTF("Hello NDK");}

extern "C" { JNIEXPORT jstring JNICALL Java_cookbook_chapter3_HelloNDKEclipseActivity_getString(JNIEnv* env, jobject o){ return getString(env); }}```

将 HelloNDKEclipseActivity.java 的内容更改为以下内容。

```cpppackage cookbook.chapter3;

import android.os.Bundle;import android.app.Activity;import android.widget.TextView;

public class HelloNDKEclipseActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); TextView tv = new TextView(this); tv.setTextSize(30); tv.setText(getString()); this.setContentView(tv); } public native String getString(); static { System.loadLibrary("HelloNDKEclipse"); }}```

右键点击HelloNDKEclipse项目，选择建设项目。这将为我们建立原生库。

Right-click on the project, go to Run As, and select Android Application. The phone screen will display something similar to the following screenshot:

在HelloNDKMultipleABI.cpp文件中增加以下内容:

```cpp

jstring getString(JNIEnv* env) { return env->NewStringUTF("Hello NDK");}

extern "C" { JNIEXPORT jstring JNICALL Java_cookbook_chapter3_HelloNDKMultipleABIActivity_getString(JNIEnv* env, jobject o){ return getString(env); }}```

将HelloNDKMultipleABIActivity.java文件更改为以下内容:

```cpppackage cookbook.chapter3;

import android.os.Bundle;import android.app.Activity;import android.widget.TextView;

public class HelloNDKMultipleABIActivity extends Activity {

@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); TextView tv = new TextView(this); tv.setTextSize(30); tv.setText(getString()); this.setContentView(tv); } public native String getString(); static { System.loadLibrary("HelloNDKMultipleABI"); }}```

在 项目的jni文件夹下添加一个名为Application.mk的新文件，内容如下:

cppAPP_ABI := armeabi armeabi-v7a

右键点击HelloNDKMultipleABIActivity项目，选择建设项目。这将为我们建立原生库。

Create two emulators, with ABI set to armeabi and armeabi-v7a respectively. The following screenshot depicts how an emulator is created with the armeabi ABI:

Run the sample Android application on the two emulators. The same result is shown on both of them:

将Application.mk的内容更改为以下代码片段，并在两个 仿真器上运行示例应用。应用仍然可以在两个模拟器上工作:

```cpp

APP_ABI := armeabi```

将Application.mk的内容修改如下:

```cpp

APP_ABI := armeabi-v7a```

Run the sample application on the two emulators. The application works on the armeabi-v7a emulator, but crashes on armeabi emulator, as shown in the following screenshot:

At Eclipse, click on File | New | Other. Select Android Project from Existing Code under Android as shown in the following screenshot. Then click on Next:

浏览至安卓 NDK 文件夹的samples/hello-neon文件夹。然后点击完成。

Run the Android project on different devices and emulators. Based on your device/emulator ABI and availability of the NEON feature, you should be able to see the results as follows:

• For Android device with armeabi ABI, the result is as follows:

• 对于搭载 armeabi-v7a ABI 和 NEON 的安卓设备，结果如下:

在Android.mk的静态库列表中添加如下:

cppLOCAL_STATIC_LIBRARIES := cpufeatures

在Android.mk文件的末尾，导入cpufeatures模块:

cpp$(call import-module,cpufeatures)

在代码中，包含头文件。

Get the CPU family. The function prototype is as follows:

cppAndroidCpuFamily android_getCpuFamily();

它返回一个枚举。受支持的 CPU 系列在下面的部分列出。

cppANDROID_CPU_FAMILY_MIPS ANDROID_CPU_FAMILY_MIPS ANDROID_CPU_FAMILY_ARM

获得可选的中央处理器功能。每个中央处理器功能由一个位标志表示，如果该功能可用，该位将被设置为1。功能原型如下:

cppuint64_t android_getCpuFeatures();

在jni文件夹下添加一个名为mylog.h的新文件，并添加以下内容:

```cpp

```

在NDKLoggingDemo.cpp中增加以下 内容:

```cpp

void outputLogs() { LOGU(9, "unknown log message"); LOGD(8, "default log message"); LOGV(7, "verbose log message"); LOGDE(6, "debug log message"); LOGI(5, "information log message"); LOGW(4, "warning log message"); LOGE(3, "error log message"); LOGF(2, "fatal error log message"); LOGS(1, "silent log message");}

extern "C" { JNIEXPORT void JNICALL Java_cookbook_chapter3_NDKLoggingDemoActivity_LoggingDemo(JNIEnv* env, jobject o){ outputLogs(); }}```

将NDKLoggingDemoActivity.java的 内容改为如下:

```cpppackage cookbook.chapter3;

import android.os.Bundle;import android.app.Activity;

public class NDKLoggingDemoActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); LoggingDemo(); } public native void LoggingDemo(); static { System.loadLibrary("NDKLoggingDemo"); }}```

将Android.mk文件更改为包含安卓日志库，如下所示:

```cppLOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := NDKLoggingDemoLOCAL_SRC_FILES := NDKLoggingDemo.cppLOCAL_LDLIBS := -lloginclude $(BUILD_SHARED_LIBRARY)```

右键点击NDKLoggingDemo项目，选择建设项目。

Start the monitor logcat output by entering the following command. Then, start the sample Android app on an Android device:

```cpp$ adb logcat -c$ adb logcat NDKLoggingDemo:I *:S -v time

```

以下是 logcat 输出的屏幕截图:

Start another command line terminal, and enter the following command in it:

```cpp$ adb logcat NDKLoggingDemo:V *:S -v time

```

这将导致以下输出:

将mylog.h中的线路从#define LOG_LEVEL 9改为#define LOG_LEVEL 4。重建应用，然后重新启动应用。

The outputs of the two terminals we started earlier are the same.

将CheckJNIDemoActivity.java改为如下:

```cpppackage cookbook.chapter3;import android.os.Bundle;import android.app.Activity;

public class CheckJNIDemoActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_check_jnidemo); CheckJNIDemo(); } public native int[] CheckJNIDemo(); static { System.loadLibrary("CheckJNIDemo"); }}```

右键点击CheckJNIDemo项目，选择建设项目。

Start the monitor logcat output by entering "adb logcat -v time" on a command-line console. Then, start the sample Android app on an Android device. The application will crash, and the logcat output will be displayed as follows:

启用 CheckJNI。

• 当您正在使用模拟器时，默认情况下 CheckJNI 是打开的。

• 如果您使用的是根设备，以下命令序列可用于在启用 CheckJNI 的情况下重启 运行时。这些命令停止正在运行的 Android 实例，更改系统属性以启用 CheckJNI，然后重新启动 Android。

  ```cpp$ adb shell stop$ adb shell setprop dalvik.vm.checkjni true$ adb shell start

  ```

• 如果您有常规设备，可以使用以下命令:

  ```cpp$ adb shell setprop debug.checkjni 1

  ```

Run the Android application again. The logcat output will be displayed as follows:

将以下代码添加到HelloNDKGDB.cpp :

```cpp

int multiply(int i, int j) { int x = i * j; return x;}

extern "C" { JNIEXPORT jint JNICALL Java_cookbook_chapter3_HelloNDKGDBActivity_multiply(JNIEnv* env, jobject o, jint pi, jint pj){ int i = 1, j = 0; while (i) { j=(++j)/100;

}return multiply(pi, pj);

}}```

将HelloNDKGDBActivity.java 的内容改为如下:

```cpppackage cookbook.chapter3;

import android.os.Bundle;import android.widget.TextView;import android.app.Activity;

public class HelloNDKGDBActivity extends Activity {

@Overridepublic void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); TextView tv = new TextView(this); tv.setTextSize(30); tv.setText("10 x 20 = " + multiply(10, 20)); this.setContentView(tv); } public native int multiply(int a, int b); static { System.loadLibrary("HelloNDKGDB"); }}```

确保AndroidManifest.xml中的debuggable 属性设置为true。以下代码片段是从我们的示例项目AndroidManifest.xml中提取的应用元素的一部分:

cpp android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" android:debuggable="true" >

使用命令“ndk-build NDK_DEBUG=1”构建本机库。或者，我们可以在项目属性的 C/C++ Build 下的 Eclipse 中配置build命令。这在 Eclipse 的调试安卓 NDK 应用食谱中有所展示。

在安卓设备上运行应用。然后，启动一个终端，输入以下命令:

```cpp$ ndk-gdb

```

Once the debugger is attached to the remote process, we can issue GDB commands to start debugging the app. This is shown as follows:

Make a copy of the ndk-gdb script under the Android NDK root directory. This can be done with the following command:

```cpp$ cp $ANDROID_NDK/ndk-gdb $ANDROID_NDK/ndk-cgdb

```

这里，$ANDROID_NDK指的是安卓 NDK root目录。

Change the following line in the ndk-cgdb script from:

```cppGDBCLIENT=${TOOLCHAIN_PREFIX}gdb

```

致:

```cppGDBCLIENT="cgdb -d ${TOOLCHAIN_PREFIX}gdb --"

```

We'll use the project created in the Debugging Android NDK application with NDK GDB recipe. If you don't have the project open in your Eclipse IDE, click on File | Import. Select Existing Projects into Workspace under General, then click on Next. In the import window, check Select root directory, and browse to the HelloNDKGDB project. Click on Finish to import the project:

Run the application on an Android device. Then, start a termina, and enter the following command:

```cppndk-cgdb

```

以下为cgdb界面截图:

我们可以发出gdb命令。注意，窗口上半部分会用箭头标记当前执行行，所有断点用红色标记。

We'll use the project created in the Building Android NDK application at Eclipse recipe. If you don't have the project open in your Eclipse IDE, click on File | Import. Select Existing Projects into Workspace under General, then click on Next. In the import window, check Select root directory, and browse to the HelloNDKEclipse project. Click on Finish to import the project:

右键点击HelloNDKEclipse项目，选择属性。在属性窗口中，选择 C/C++构建。取消选中使用默认构建命令，将构建命令更改为ndk-build NDK_DEBUG=1。

Click on OK to dismiss the window:

Add the following code before the native method is called at HelloNDKEclipseActivity.java.

在HelloNDKEclipse.cpp中设置两个断点:

Right-click on your project and then select Debug As | Android Native Application. We'll see if the breakpoints are hit.