如何将文件路径从.java类文件传递到本机jni文件

I want to pass a file path from Java class to native file using jni. In the native implementation file I want to check if file exists or not.

我想使用jni将文件路径从Java类传递到本机文件。在本机实现文件中,我想检查文件是否存在。

This is my java file:

这是我的java文件:

public class FileNative extends Activity {

    String fpath = "storage/emulated/0/Download/view.pdf";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = (Button)findViewById(R.id.button1);
        button.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            String str1 =null;
            Log.d("Click","The button has been clicked to open the file");
            str1 = ndkopenfile(fpath);
        }
    }

    public native String ndkopenfile(String fpath);

    static {
        System.loadLibrary("file-jni");
    }
}

This is my C++ file:

这是我的C ++文件:

JNIEXPORT jstring JNICALL Java_com_example_filewithnative_FileNative_ndkopenfile(JNIEnv *env, jobject obj , jstring path)
{
    const char* jnamestr = env->GetStringUTFChars(path, 0);
    char retPath[20];
    FILE* fp = fopen(jnamestr,"w+");
    if(fp)
    {
        return env->NewStringUTF(jnamestr);
    }
    else
    {
        return env->NewStringUTF("Error opening file!");
    }
}

Please help me figure out why this isn't working. Thanks!

请帮我弄清楚为什么这不起作用。谢谢!

1 个解决方案

#1

first of all,

首先,

public native String ndkopenfile(String fpath); static{ System.loadLibrary("file-jni"); }

public native String ndkopenfile(String fpath); static {System.loadLibrary(“file-jni”); }

should be within your FileNative class. Second, you'll have to compile your native code as a static library for whatever architectures you want to support (ex: armeabi, armeabi-v7a, x86) and put them in the appropriate directories within the apk.

应该在你的FileNative类中。其次,您必须将您的本机代码编译为您想要支持的任何体系结构的静态库(例如:armeabi,armeabi-v7a,x86),并将它们放在apk中的相应目录中。

You should really read up on the Android NDK and maybe run through a tutorial or two. https://developer.android.com/tools/sdk/ndk/index.html#GetStarted

您应该阅读Android NDK并且可能会通过一两个教程来阅读。 https://developer.android.com/tools/sdk/ndk/index.html#GetStarted

1 个解决方案

#1

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