如何從.c文件內部調用NDK方法？

Question

我有我的GNUTLS內的方法.c文件如下

int gnutls_error_is_fatal (int error) 
     { 
    int ret = 1; 
    const gnutls_error_entry *p; 

    /* Input sanitzation. Positive values are not errors at all, and 
    definitely not fatal. */ 
    if (error > 0) 
    return 0; 

    for (p = error_algorithms; p->desc != NULL; p++) 
    { 
    if (p->number == error) 
     { 
     ret = p->fatal; 
     break; 
     } 
     } 

     return ret; 
     } 

如何定義它在我的活動類的內部，使得我能夠使用它，並得到一個返回值？

我試過

 private native int gnutls_error_is_fatal(int i); 


    @Override 
     public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

     // this is where we call the native code 
     int hello = gnutls_error_is_fatal(1); 

，但它不能正常工作

提供了以下錯誤

E/AndroidRuntime( 756): FATAL EXCEPTION: main 
E/AndroidRuntime( 756): java.lang.ExceptionInInitializerError 
E/AndroidRuntime( 756): at java.lang.Class.newInstanceImpl(Native Method) 
E/AndroidRuntime( 756): at java.lang.Class.newInstance(Class.java:1409) 
E/AndroidRuntime( 756): at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 
E/AndroidRuntime( 756): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561) 
E/AndroidRuntime( 756): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 
E/AndroidRuntime( 756): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 
E/AndroidRuntime( 756): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 
E/AndroidRuntime( 756): at android.os.Handler.dispatchMessage(Handler.java:99) 
E/AndroidRuntime( 756): at android.os.Looper.loop(Looper.java:123) 
E/AndroidRuntime( 756): at android.app.ActivityThread.main(ActivityThread.java:3683) 
E/AndroidRuntime( 756): at java.lang.reflect.Method.invokeNative(Native Method) 
E/AndroidRuntime( 756): at java.lang.reflect.Method.invoke(Method.java:507) 
E/AndroidRuntime( 756): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
E/AndroidRuntime( 756): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
E/AndroidRuntime( 756): at dalvik.system.NativeStart.main(Native Method) 
E/AndroidRuntime( 756): Caused by: java.lang.UnsatisfiedLinkError: Couldn't load REALGnuTLS: findLibrary returned null 
E/AndroidRuntime( 756): at java.lang.Runtime.loadLibrary(Runtime.java:429) 
E/AndroidRuntime( 756): at java.lang.System.loadLibrary(System.java:554) 
E/AndroidRuntime( 756): at com.test.example.REALGnuTLSActivity.<clinit>(REALGnuTLSActivity.java:12) 

Answer 1

你有沒有正確地構建本地庫，併產生JNI頭？

看看這個教程：

http://marakana.com/forums/android/examples/49.html

這是有點過時，但一般的方法仍然應該是相同的。