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PONo JNI_OnLoad and no return value from native function?
 

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  1. PONo JNI_OnLoad and no return value from native function?
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    <p>i need to make linux command from native method by c++ code.</p> <p>this is my class <b>Test.java</b></p> <pre><code>public class Test { static { System.loadLibrary("NDK1"); } public native String exec(String cmd); } </code></pre> <p>then i create header .h by this command :</p> <pre><code>$ javah -classpath ../bin/classes com.example.new1.Test </code></pre> <p>after this the header .h is created in this path com.example.new1 then i create <b>jni</b> file and copy .h file and create .cpp file and include .h in it.</p> <pre><code>#include &lt;string&gt; #include &lt;iostream&gt; #include &lt;stdio.h&gt; #include &lt;jni.h&gt; #include "com_example_new1_Test.h" std::string exec(const char* cmd) { FILE* pipe = popen(cmd, "r"); if (!pipe) return "ERROR"; char buffer[128]; std::string result = ""; while(!feof(pipe)) { if(fgets(buffer, 128, pipe) != NULL) result += buffer; } pclose(pipe); return result; </code></pre> <p>}</p> <pre><code> JNIEXPORT jstring JNICALL Java_com_example_new1_Test_exec(JNIEnv* env, jobject javaThis , jstring cmd) { const char * res; //res = env-&gt;GetStringUTFChars(cmd ) ; // const char* utf_string; jboolean isCopy; res = env-&gt;GetStringUTFChars(cmd, &amp;isCopy); /* ... use string ... */ if (isCopy == JNI_TRUE) { (env)-&gt;ReleaseStringUTFChars(cmd, res); } std::string result = exec(res); return (env)-&gt;NewStringUTF((const char* )result.c_str()); } </code></pre> <p>then call <b>NDK </b></p> <pre><code>$ /cygdrive/c/android-ndk-r4/ndk-build make: Warning: File `/cygdrive/c/android-ndk-r4/build/core/import-locals.mk' has modification time 140582392 s in the future Cygwin : Generating dependency file converter script Compile++ thumb : NDK1 &lt;= NDK1.cpp Prebuilt : libgnustl_static.a &lt;= &lt;NDK&gt;/sources/cxx-stl/gnu- libstdc++/4.6/libs/armeabi/ SharedLibrary : libNDK1.so Install : libNDK1.so =&gt; libs/armeabi/libNDK1.so Compile++ thumb : NDK1 &lt;= NDK1.cpp Prebuilt : libgnustl_static.a &lt;= &lt;NDK&gt;/sources/cxx-stl/gnu- libstdc++/4.6/libs/armeabi-v7a/ SharedLibrary : libNDK1.so Install : libNDK1.so =&gt; libs/armeabi-v7a/libNDK1.so make: warning: Clock skew detected. Your build may be incomplete. </code></pre> <p>when i run my app there is no error or exception occurred but there is no value return from native method!! this is the log for run </p> <pre><code>03-03 22:59:55.343: E/SpannableStringBuilder(9257): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length 03-03 22:59:55.343: E/SpannableStringBuilder(9257): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length 03-03 23:00:08.527: E/Trace(9852): error opening trace file: No such file or directory (2) 03-03 23:00:08.717: D/libEGL(9852): loaded /system/lib/egl/libEGL_mali.so 03-03 23:00:08.727: D/libEGL(9852): loaded /system/lib/egl/libGLESv1_CM_mali.so 03-03 23:00:08.727: D/libEGL(9852): loaded /system/lib/egl/libGLESv2_mali.so 03-03 23:00:08.747: D/OpenGLRenderer(9852): Enabling debug mode 0 03-03 23:00:21.960: D/dalvikvm(9852): Trying to load lib /data/data/com.example.new1/lib/libNDK1.so 0x41a1d8f8 03-03 23:00:21.980: D/dalvikvm(9852): Added shared lib /data/data/com.example.new1/lib/libNDK1.so 0x41a1d8f8 03-03 23:00:21.980: D/dalvikvm(9852): No JNI_OnLoad found in /data/data/com.example.new1/lib/libNDK1.so 0x41a1d8f8, skipping init </code></pre> <blockquote> <blockquote> <p>what is the problem ? by the way, i pass "iwconfig" as linux command, is it depend on what is the command ? also do i need any permission at AndroidManifest ?</p> </blockquote> </blockquote>
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    1. USHana90
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      1. VTUpMod
    1. COHave you considered testing with a simpler JNI function, such as one that returns "Hello, world!"?
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      1. USCommonsWare
    2. COyes try this, the no JNI_Onload warning is not a matter, your lib seems well loaded.
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      1. USGuian
    3. COwhat should i try ? i didn't get it!
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      1. USHana90
 

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