java - Android, Native 开发包 : No implementation found for native Lcom/example/hellojni/Mainactivity;. sayHelloWorld ()Ljava/lang/String;

Question

好吧，那么...到此为止了。

尝试学习使用 native 开发工具包...从 C 源返回字符串“Hello World”时的 Hello World 开始。

开始:这是“主要 Activity ”。

package com.example.hellojni;

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

public class MainActivity extends Activity {

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

        TextView textView=(TextView) findViewById(R.id.text1);

        textView.setText(sayHelloWorld());
    }


    private native String sayHelloWorld();

    @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;
    }

    static {
        System.loadLibrary("HelloJni");
    }

}

为了完整起见，这里是定义显示的 XML。我敢打赌这不是问题所在，但如果我不提它就是学术上的疏忽。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/text1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="@string/hello_world" />

</RelativeLayout>

接下来，当然需要javah生成的头文件了。

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_example_hellojni_MainActivity */

#ifndef _Included_com_example_hellojni_MainActivity
#define _Included_com_example_hellojni_MainActivity
#ifdef __cplusplus
extern "C" {
#endif
#undef com_example_hellojni_MainActivity_MODE_PRIVATE
#define com_example_hellojni_MainActivity_MODE_PRIVATE 0L
#undef com_example_hellojni_MainActivity_MODE_WORLD_READABLE
#define com_example_hellojni_MainActivity_MODE_WORLD_READABLE 1L
#undef com_example_hellojni_MainActivity_MODE_WORLD_WRITEABLE
#define com_example_hellojni_MainActivity_MODE_WORLD_WRITEABLE 2L
#undef com_example_hellojni_MainActivity_MODE_APPEND
#define com_example_hellojni_MainActivity_MODE_APPEND 32768L
#undef com_example_hellojni_MainActivity_MODE_MULTI_PROCESS
#define com_example_hellojni_MainActivity_MODE_MULTI_PROCESS 4L
#undef com_example_hellojni_MainActivity_MODE_ENABLE_WRITE_AHEAD_LOGGING
#define com_example_hellojni_MainActivity_MODE_ENABLE_WRITE_AHEAD_LOGGING 8L
#undef com_example_hellojni_MainActivity_BIND_AUTO_CREATE
#define com_example_hellojni_MainActivity_BIND_AUTO_CREATE 1L
#undef com_example_hellojni_MainActivity_BIND_DEBUG_UNBIND
#define com_example_hellojni_MainActivity_BIND_DEBUG_UNBIND 2L
#undef com_example_hellojni_MainActivity_BIND_NOT_FOREGROUND
#define com_example_hellojni_MainActivity_BIND_NOT_FOREGROUND 4L
#undef com_example_hellojni_MainActivity_BIND_ABOVE_CLIENT
#define com_example_hellojni_MainActivity_BIND_ABOVE_CLIENT 8L
#undef com_example_hellojni_MainActivity_BIND_ALLOW_OOM_MANAGEMENT
#define com_example_hellojni_MainActivity_BIND_ALLOW_OOM_MANAGEMENT 16L
#undef com_example_hellojni_MainActivity_BIND_WAIVE_PRIORITY
#define com_example_hellojni_MainActivity_BIND_WAIVE_PRIORITY 32L
#undef com_example_hellojni_MainActivity_BIND_IMPORTANT
#define com_example_hellojni_MainActivity_BIND_IMPORTANT 64L
#undef com_example_hellojni_MainActivity_BIND_ADJUST_WITH_ACTIVITY
#define com_example_hellojni_MainActivity_BIND_ADJUST_WITH_ACTIVITY 128L
#undef com_example_hellojni_MainActivity_CONTEXT_INCLUDE_CODE
#define com_example_hellojni_MainActivity_CONTEXT_INCLUDE_CODE 1L
#undef com_example_hellojni_MainActivity_CONTEXT_IGNORE_SECURITY
#define com_example_hellojni_MainActivity_CONTEXT_IGNORE_SECURITY 2L
#undef com_example_hellojni_MainActivity_CONTEXT_RESTRICTED
#define com_example_hellojni_MainActivity_CONTEXT_RESTRICTED 4L
#undef com_example_hellojni_MainActivity_RESULT_CANCELED
#define com_example_hellojni_MainActivity_RESULT_CANCELED 0L
#undef com_example_hellojni_MainActivity_RESULT_OK
#define com_example_hellojni_MainActivity_RESULT_OK -1L
#undef com_example_hellojni_MainActivity_RESULT_FIRST_USER
#define com_example_hellojni_MainActivity_RESULT_FIRST_USER 1L
#undef com_example_hellojni_MainActivity_DEFAULT_KEYS_DISABLE
#define com_example_hellojni_MainActivity_DEFAULT_KEYS_DISABLE 0L
#undef com_example_hellojni_MainActivity_DEFAULT_KEYS_DIALER
#define com_example_hellojni_MainActivity_DEFAULT_KEYS_DIALER 1L
#undef com_example_hellojni_MainActivity_DEFAULT_KEYS_SHORTCUT
#define com_example_hellojni_MainActivity_DEFAULT_KEYS_SHORTCUT 2L
#undef com_example_hellojni_MainActivity_DEFAULT_KEYS_SEARCH_LOCAL
#define com_example_hellojni_MainActivity_DEFAULT_KEYS_SEARCH_LOCAL 3L
#undef com_example_hellojni_MainActivity_DEFAULT_KEYS_SEARCH_GLOBAL
#define com_example_hellojni_MainActivity_DEFAULT_KEYS_SEARCH_GLOBAL 4L
/*
 * Class:     com_example_hellojni_MainActivity
 * Method:    sayHelloWorld
 * Signature: ()Ljava/lang/String;
 */
JNIEXPORT jstring JNICALL Java_com_example_hellojni_MainActivity_sayHelloWorld (JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

接下来自然要看的是 C 源代码....

#include "com_example_hellojni_MainActivity.h"

jstring Java_com_example_HelloWorldActivity_sayHelloWorld(JNIEnv* pEnv, jobject thiz) {

    return (pEnv->NewStringUTF("Hello World from C!"));

    //return (*pEnv)->NewStringUTF(env,"Hello World from C!");
}

评论版本，我不记得我从哪里得到的......可能是从一本书中转录出来的。无论如何，它甚至没有编译。我使用的版本对我来说更有意义。也许这就是问题所在。

接着，这里是android.mk:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := HelloJni
LOCAL_SRC_FILES := HelloJni.cpp

include $(BUILD_SHARED_LIBRARY)

当然...当我将所有这些放在一起时，我得到了一个可以编译并尝试运行的 apk。下面是我已经拔头发好几天的笑话的妙语:

03-22 21:34:38.218: I/ActivityManager(322): Start proc com.example.hellojni for activity com.example.hellojni/.MainActivity: pid=20945 uid=10175 gids={}
03-22 21:34:38.278: D/dalvikvm(20945): Trying to load lib /data/data/com.example.hellojni/lib/libHelloJni.so 0x417260f0
03-22 21:34:38.278: D/dalvikvm(20945): Added shared lib /data/data/com.example.hellojni/lib/libHelloJni.so 0x417260f0
03-22 21:34:38.278: D/dalvikvm(20945): No JNI_OnLoad found in /data/data/com.example.hellojni/lib/libHelloJni.so 0x417260f0, skipping init
03-22 21:34:38.318: W/dalvikvm(20945): No implementation found for native Lcom/example/hellojni/MainActivity;.sayHelloWorld ()Ljava/lang/String;
03-22 21:34:38.328: E/AndroidRuntime(20945):    at com.example.hellojni.MainActivity.sayHelloWorld(Native Method)
03-22 21:34:38.328: E/AndroidRuntime(20945):    at com.example.hellojni.MainActivity.onCreate(MainActivity.java:17)
03-22 21:34:38.328: W/ActivityManager(322):   Force finishing activity com.example.hellojni/.MainActivity
03-22 21:34:38.868: W/ActivityManager(322): Activity pause timeout for ActivityRecord{4235a518 com.example.hellojni/.MainActivity}
03-22 21:34:49.008: W/ActivityManager(322): Activity destroy timeout for ActivityRecord{4235a518 com.example.hellojni/.MainActivity}
03-22 21:34:56.208: I/ActivityManager(322): Process com.example.hellojni (pid 20945) has died.

请帮忙。沮丧是巨大的，理智正在消退。

Answer 1

Praful Bhatnagar 的评论恰到好处。我修复了困扰我的错误，其他一切都归于原位。谢谢!

(不确定我是否应该做些什么来正确地将答案归因于说它的人)