android ndk程序获取外置SD沙盒目录的方法讲解

Android NDK程序获取外置SD沙盒目录的方法讲解

在Android NDK程序中，要获取外置SD卡的沙盒目录，可以按照以下步骤进行：

1. 首先，确保你的应用已经声明了读取外部存储的权限。在AndroidManifest.xml文件中添加以下权限声明：

<uses-permission android:name=\"android.permission.READ_EXTERNAL_STORAGE\" />

1. 在你的NDK代码中，使用以下方法获取外置SD卡的路径：

#include <jni.h>
#include <android/native_activity.h>
#include <android/asset_manager.h>
#include <android/asset_manager_jni.h>
#include <android/log.h>

extern \"C\" JNIEXPORT jstring JNICALL
Java_com_example_ndkexample_MainActivity_getExternalSdCardPath(JNIEnv* env, jobject /* this */, jobject activity) {
    jclass activityClass = env->GetObjectClass(activity);
    jmethodID getExternalFilesDirMethod = env->GetMethodID(activityClass, \"getExternalFilesDir\", \"(Ljava/lang/String;)Ljava/io/File;\");
    jstring nullString = env->NewStringUTF(NULL);
    jobject externalFilesDir = env->CallObjectMethod(activity, getExternalFilesDirMethod, nullString);
    jclass fileClass = env->FindClass(\"java/io/File\");
    jmethodID getPathMethod = env->GetMethodID(fileClass, \"getPath\", \"()Ljava/lang/String;\");
    jstring pathString = (jstring)env->CallObjectMethod(externalFilesDir, getPathMethod);
    return pathString;
}

1. 在你的Java代码中，调用上述NDK方法来获取外置SD卡的路径：

public class MainActivity extends AppCompatActivity {
    static {
        System.loadLibrary(\"your-ndk-library\");
    }

    public native String getExternalSdCardPath();

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

        String sdCardPath = getExternalSdCardPath();
        Log.d(\"MainActivity\", \"External SD Card Path: \" + sdCardPath);
    }
}

这样，你就可以在你的NDK程序中获取到外置SD卡的沙盒目录了。

示例说明：

1. 示例1：获取外置SD卡的根目录

public class MainActivity extends AppCompatActivity {
    static {
        System.loadLibrary(\"your-ndk-library\");
    }

    public native String getExternalSdCardPath();

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

        String sdCardPath = getExternalSdCardPath();
        Log.d(\"MainActivity\", \"External SD Card Path: \" + sdCardPath);

        File sdCardRoot = new File(sdCardPath);
        Log.d(\"MainActivity\", \"External SD Card Root: \" + sdCardRoot.getAbsolutePath());
    }
}

1. 示例2：在外置SD卡上创建一个新文件夹

public class MainActivity extends AppCompatActivity {
    static {
        System.loadLibrary(\"your-ndk-library\");
    }

    public native String getExternalSdCardPath();

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

        String sdCardPath = getExternalSdCardPath();
        Log.d(\"MainActivity\", \"External SD Card Path: \" + sdCardPath);

        File sdCardRoot = new File(sdCardPath);
        File newFolder = new File(sdCardRoot, \"MyFolder\");
        if (!newFolder.exists()) {
            if (newFolder.mkdirs()) {
                Log.d(\"MainActivity\", \"New folder created: \" + newFolder.getAbsolutePath());
            } else {
                Log.d(\"MainActivity\", \"Failed to create new folder\");
            }
        } else {
            Log.d(\"MainActivity\", \"Folder already exists: \" + newFolder.getAbsolutePath());
        }
    }
}

以上就是获取外置SD卡沙盒目录的方法讲解，希望对你有所帮助！