What does "can't get it to work" mean?
Is mActivity really a reference to the correct activity?
Does is successfully find the method, or take the 'return false;'
exit? (Which is rather odd in a void method!)
Does it crash?
Does it call the Java code, but with a corrupted message?
If it's that last, I'd look for the usual C++ headaches, such as using
a std::string() that has been destructed by the time you use it.
If it's crashing: Where is it crashing? How is mJNIEnv declared and
assigned?
Have you stepped through it in a debugger? I don't know hard that is
to do on a device (or emulator) with the NDK, but you could certainly
write a little test app on your PC and test the C++ side there. You'd
have to substitute on the Java side, of course; a simple
System.out.println("Success: " + pMsg); would suffice.
If none of that helps, I'd suggest asking the question in a list that
relates to the NDK rather than the SDK. You'd find a larger pool of
people able to understand and answer your questions on the topic.
On Dec 14, 10:30 am, Floof <[email protected]> wrote:
> Hi list !
>
> I'm having this problem:
>
> In my application, I use a GLSurfaceView for 3D rendering. The real
> rendering is done by calling native methods, coded in C++.
>
> Once in a while (upon user clicks on 3D scene objects) the native
> rendering engine should be able to call Java methods (through JNI)
> that display a dialog box.
>
> I can't get it to work, that's driving me crazy.
>
> Here is the native method:
>
> [CODE]
> void MyCPlusPlusClass::showDialog(const std::string& pMsg)
> {
> jclass lClass = mJNIEnv->GetObjectClass(mActivity);
> if (!lClass)
> {
> return false;
> }
> jmethodID lMethId = mJNIEnv->GetMethodID(lClass,
> "showMessageDialog", "(Ljava/lang/String;)V");
> if (!lMethId)
> {
> return false;
> }
> jstring lJavaString = mJNIEnv->NewStringUTF(pMessage.c_str());
> mJNIEnv->CallVoidMethod(mActivity, lMethId, lJavaString);}
>
> [/CODE]
>
> Then, the method showMessageDialog, coded in Java, in my activity:
>
> [CODE]
> public void showMessageDialog(String pMsg)
> {
> Log.i("Vg", "Create dialog with message " + pMsg);
> Log.i("Vg", "Show dialog");
> runOnUiThread(
> new Runnable () {
> public void run () {
> AlertDialog.Builder lAlertBox = new
> AlertDialog.Builder(this);
> TextView lTextView = new TextView(MyActivity.this);
> lTextView.setText(mMessage);
> lAlertBox.setView(lTextView);
> lAlertBox.setNeutralButton("Ok", MyActivity.this);
> lAlertBox.setOnCancelListener(MyActivity.this);
> lAlertBox.show();
> }
> }
> );}
>
> [/CODE]
>
> I thought this would work, but it doesn't. What am I doing wrong ?
>
> Thanks
> Florent.
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