Apps Android NDK + pthread - applciation crash

[Leshik]

Hello everyone.
I am never programming to Android, this is my first application.
I create simpla application with two threads:
first - Java UI thread, and second thread created by calling native function from Java code.
I want call Java function for print text in TextView, but when I call env->FindClass("test/app/Test"); application did crashed http://img706.imageshack.us/img706/7047/screenshot20100113at145.png.
the AttachCurrentThread return 0.

this is example of my native code:

#include "test.h"
#include <pthread.h>
#include <stdlib.h>
#include <stdio.h>

JavaVM* g_jvm = 0;

JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void * reserved)
{
    g_jvm = vm;
    return JNI_VERSION_1_6;
}

void JNI_OnUnload(JavaVM *vm, void *reserved)
{
    g_jvm = 0;
}

void* threadProc(void*)
{
    JNIEnv* env = 0;
    int res = g_jvm->AttachCurrentThread(&env, NULL); // res == 0
    
    jclass jclsTest = env->FindClass("test/app/Test"); // if comment this line, application not crashed
    
    g_jvm->DetachCurrentThread();
    env = 0;
    
    return 0;
}

JNIEXPORT jboolean JNICALL Java_test_app_Test_initialize(JNIEnv* env, jobject obj)
{
    jclass jcls = env->FindClass("test/app/Test");
    jmethodID mid = env->GetMethodID(jcls, "messageOutput", "(Ljava/lang/String;)V");
    
    env->CallVoidMethod(obj, mid, env->NewStringUTF("start thread"));
    
    pthread_t thread = 0;
    pthread_create(&thread, NULL, threadProc, NULL);
    
    env->CallVoidMethod(obj, mid, env->NewStringUTF("thread started"));
    
    return true;
}

 

[KeithG]

first, 0 != NULL Don't assign scalars to pointers...

In threadProc(), your throwing away the result of the AttachCurrentThread(). How do you know env has be set properly?

I would guess that deferencing the FindClass() method via the env object is failing because env may be NULL.

 

[Leshik]

Thanks for your reply, but code with some changes also not work

If comment line
jclass jclsTest = env->FindClass("test/app/Test");
application not crashed.

#include "test.h"
#include <pthread.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

JavaVM* g_jvm = NULL;

JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void * reserved)
{
    g_jvm = vm;
    return JNI_VERSION_1_6;
}

void JNI_OnUnload(JavaVM *vm, void *reserved)
{
    g_jvm = NULL;
}

void* threadProc(void*)
{
    sleep(10);
    if(g_jvm == NULL)
    {
        return NULL;
    }
    
    JNIEnv* env = NULL;
    g_jvm->AttachCurrentThread(&env, NULL);
    
    if(env == NULL)
    {
        return NULL;
    }
    
    jclass jclsTest = env->FindClass("test/app/Test");
    
    g_jvm->DetachCurrentThread();
    
    return NULL;
}

JNIEXPORT jboolean JNICALL Java_test_app_Test_initialize(JNIEnv* env, jobject obj)
{
    if(g_jvm == NULL)
    {
        return JNI_FALSE;
    }
    
    g_jvm->AttachCurrentThread(&env, NULL);
    
    if(env == NULL)
    {
        return JNI_FALSE;
    }
    
    jclass jcls = env->FindClass("test/app/Test");
    jmethodID mid = env->GetMethodID(jcls, "messageOutput", "(Ljava/lang/String;)V");
    
    env->CallVoidMethod(obj, mid, env->NewStringUTF("thread start"));
    
    pthread_t thread = 0;
    pthread_create(&thread, NULL, threadProc, NULL);
    pthread_join(thread, NULL);
    
    env->CallVoidMethod(obj, mid, env->NewStringUTF("thread finish"));
    
    
    return JNI_TRUE;
}

 

[Leshik]

if I change
jclass jclsTest = env->FindClass("test/app/Test"); in void* threadProc(void*) function by
jclass jclsview = env->FindClass("android/widget/TextView");
programm not crashed,
may be I am not maked some actions with Test class ?

this is implementation of Test class:

package test.app;

import android.app.Activity;
import android.os.Bundle;
import android.text.format.Time;
import android.widget.TextView;

public class Test extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        initialize();
    }
...
...

 

[leewind]

What do you mean 'Crash'? Can you support the log information. I think the problem here should be happened in android.mk. Can you post your android.mk?