Android Java NDK/JNI - UnsatisfiedLinkError：未找到本地方法[...] Ljava/lang/String;

Question

我的程序旨在成爲一個簡單的程序，它使用Android NDK在android應用程序中實現一些C++代碼。該指南我按照是http://taylorpeer.com/hello-world-cpp-android-ndk/但是當我運行程序出現錯誤

java.lang.UnsatisfiedLinkError: Native method not found: com.example.spotifywidget.MainActivity.stringFromJNI:()Ljava/lang/String;

，我把它當我運行線過stringFromJNI叫我C++（）方法。波紋管我已經包括MainActivity.java

package com.example.spotifywidget; 

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

public class MainActivity extends Activity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     System.err.println("HELLO!"); 

     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 

     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.activity_main, menu); 

     return true; 
    } 
    public native String stringFromJNI();  //A string to store the return in 
    @Override 
    public void onBackPressed() { 

     System.err.println(this.stringFromJNI()); //Call the c++ method 

    } 
    static{ 
     System.loadLibrary("SpotifyWidget"); //Load the c++ library 
    } 
} 

的spotifywidget.cpp

#include <jni.h> 
#include <string.h> 
//#include <api.h> 

extern "C"{ 

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

} 

的android.mk

LOCAL_PATH := $(call my-dir) 

include $(CLEAR_VARS) 

LOCAL_MODULE := SpotifyWidget 
LOCAL_SRC_FILES := SpotifyWidget.cpp 
include $(BUILD_SHARED_LIBRARY) 

和logcat的輸出

09-28 18:25:40.176: E/Trace(991): error opening trace file: No such file or directory (2) 
09-28 18:25:40.487: D/dalvikvm(991): Trying to load lib /data/data/com.example.spotifywidget/lib/libSpotifyWidget.so 0x41196fc0 
09-28 18:25:40.487: D/dalvikvm(991): Added shared lib /data/data/com.example.spotifywidget/lib/libSpotifyWidget.so 0x41196fc0 
09-28 18:25:40.496: D/dalvikvm(991): No JNI_OnLoad found in /data/data/com.example.spotifywidget/lib/libSpotifyWidget.so 0x41196fc0, skipping init 
09-28 18:25:40.506: W/System.err(991): HELLO! 
09-28 18:25:40.766: D/libEGL(991): loaded /system/lib/egl/libEGL_emulation.so 
09-28 18:25:40.776: D/(991): HostConnection::get() New Host Connection established 0x2a0e3558, tid 991 
09-28 18:25:40.867: D/libEGL(991): loaded /system/lib/egl/libGLESv1_CM_emulation.so 
09-28 18:25:40.885: D/libEGL(991): loaded /system/lib/egl/libGLESv2_emulation.so 
09-28 18:25:40.986: W/EGL_emulation(991): eglSurfaceAttrib not implemented 
09-28 18:25:40.996: D/OpenGLRenderer(991): Enabling debug mode 0 
09-28 18:25:44.459: W/dalvikvm(991): No implementation found for native Lcom/example/spotifywidget/MainActivity;.stringFromJNI:()Ljava/lang/String; 
09-28 18:25:44.459: D/AndroidRuntime(991): Shutting down VM 
09-28 18:25:44.459: W/dalvikvm(991): threadid=1: thread exiting with uncaught exception (group=0x40a13300) 
09-28 18:25:44.466: E/AndroidRuntime(991): FATAL EXCEPTION: main 
09-28 18:25:44.466: E/AndroidRuntime(991): java.lang.UnsatisfiedLinkError: Native method not found: com.example.spotifywidget.MainActivity.stringFromJNI:()Ljava/lang/String; 
09-28 18:25:44.466: E/AndroidRuntime(991): at com.example.spotifywidget.MainActivity.stringFromJNI(Native Method) 
09-28 18:25:44.466: E/AndroidRuntime(991): at com.example.spotifywidget.MainActivity.onBackPressed(MainActivity.java:29) 
09-28 18:25:44.466: E/AndroidRuntime(991): at android.app.Activity.onKeyUp(Activity.java:2131) 
09-28 18:25:44.466: E/AndroidRuntime(991): at android.view.KeyEvent.dispatch(KeyEvent.java:2633) 
09-28 18:25:44.466: E/AndroidRuntime(991): at android.app.Activity.dispatchKeyEvent(Activity.java:2361) 
09-28 18:25:44.466: E/AndroidRuntime(991): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1819) 
09-28 18:25:44.466: E/AndroidRuntime(991): at android.view.ViewRootImpl.deliverKeyEventPostIme(ViewRootImpl.java:3577) 
09-28 18:25:44.466: E/AndroidRuntime(991): at android.view.ViewRootImpl.handleImeFinishedEvent(ViewRootImpl.java:3547) 
09-28 18:25:44.466: E/AndroidRuntime(991): at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:2797) 
09-28 18:25:44.466: E/AndroidRuntime(991): at android.os.Handler.dispatchMessage(Handler.java:99) 
09-28 18:25:44.466: E/AndroidRuntime(991): at android.os.Looper.loop(Looper.java:137) 
09-28 18:25:44.466: E/AndroidRuntime(991): at android.app.ActivityThread.main(ActivityThread.java:4745) 
09-28 18:25:44.466: E/AndroidRuntime(991): at java.lang.reflect.Method.invokeNative(Native Method) 
09-28 18:25:44.466: E/AndroidRuntime(991): at java.lang.reflect.Method.invoke(Method.java:511) 
09-28 18:25:44.466: E/AndroidRuntime(991): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
09-28 18:25:44.466: E/AndroidRuntime(991): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
09-28 18:25:44.466: E/AndroidRuntime(991): at dalvik.system.NativeStart.main(Native Method) 

感謝提前任何幫助:)

Answer 1

認爲Java_com_example_SpotifyWidget_stringFromJNI是錯誤的：

嘗試：Java_com_example_spotifywidget_MainActivity_stringFromJNI