[工作积累] Android system dialog with native callback

JNI: invoke java dialog with native callback:

store native function address in java, and invoke native another method to this function.

key points:

1.Store callback function pointer(address) in java: to support multiple calls, use data block for each call.

2.Use primitive long(64bit) in Java to store native callback pointer, for 64 bit native compatibility

3.intptr_t for pointer in native.

4.Show dialog  in UI thread (Activity.runOnUiThread )

5.optional: Let the native code to handle localization (minimize Java code)

Java:

 public static native void nativeOnSystemDialogResult(long nativeFuncAddr);

     class DialogRunnable implements Runnable {
         public String mTitle;
         public String mMessage;
         public String mYes;
         public String mNo;
         public long mOnYesAddr;
         public long mOnNoAddr;
         public boolean mTwoButton;

         //////////////////////////////////////////////////////////////////////////
         ///title, message, localized Yes No
         DialogRunnable(String tittle, String message, String locYes, String locNo, long onYesAddr, long onNoAddr, boolean twoButton)
         {
             mTitle = tittle;
             mMessage = message;
             mYes = locYes;
             mNo = locNo;
             mOnYesAddr = onYesAddr;
             mOnNoAddr = onNoAddr;
             mTwoButton = twoButton;
         }

         //////////////////////////////////////////////////////////////////////////
         public void run() {

             if( mTwoButton ) {
                 Dialog dialog = new AlertDialog.Builder( GameActivity.getInstance() )
                 .setTitle(mTitle)
                 .setMessage(mMessage)
                 .setPositiveButton( mYes, new DialogInterface.OnClickListener() {
                                                     public void onClick(DialogInterface dialog, int whichButton) {
                                                         GameActivity.getInstance().nativeOnSystemDialogResult( mOnYesAddr );
                                                     }
                                                 })
                 .setNegativeButton( mNo, new DialogInterface.OnClickListener() {
                                                     public void onClick(DialogInterface dialog, int whichButton) {
                                                         GameActivity.getInstance().nativeOnSystemDialogResult( mOnNoAddr );
                                                     }
                                                 })
                 .setCancelable(false)
                 .create();
                 dialog.show();
             }else {
                 Dialog dialog = new AlertDialog.Builder( GameActivity.getInstance() )
                 .setTitle(mTitle)
                 .setMessage(mMessage)
                 .setPositiveButton( mNo, new DialogInterface.OnClickListener() {
                                                     public void onClick(DialogInterface dialog, int whichButton) {
                                                         GameActivity.getInstance().nativeOnSystemDialogResult( mOnYesAddr );
                                                     }
                                                 })
                 .setCancelable(false)
                 .create();
                 dialog.show();
             }
         }
     }

     //////////////////////////////////////////////////////////////////////////
     //Cooperate with native code. DO NOT call on Java
     //////////////////////////////////////////////////////////////////////////
     public void showDialogYesNo(String title, String showText, String locYes, String locNo, long onYesAddr, long onNoAddr) {
         this.runOnUiThread( new DialogRunnable(title, showText, locYes, locNo, onYesAddr, onNoAddr, true) );
     }

C (for C++, JNI calls are simpler & different)

 JNIEXPORT void JNICALL Java_com_org_package_GameActivity_nativeOnSystemDialogResult(JNIEnv *env, jobject thiz, jlong functionAddr)
 {
     typedef void(*FUNCPTR)(void);
     FUNCPTR ptr = (FUNCPTR)(void*)function;
     if( ptr != null )
         ptr();
 }

 //////////////////////////////////////////////////////////////////////////
 //Note: onOK & onCancel can be NULL
 void    Android_SystemDialog(const char* title, const char* message, const char* yes, const char* no, void(*onOK)(void), void(*onCancel)(void) )
 {
     android_app* app = GetApp();
     JNIEnv* env = app->activity->env;
     //note: we need to attach dalvik VM to current thread, as it is not main thread
     JavaVM* vm = app->activity->vm;
     if ( (*vm)->GetEnv(vm, (void **)&env, JNI_VERSION_1_6) <  )
         (*vm)->AttachCurrentThread(vm, &env, NULL);

     jclass ActivityClass = (*env)->GetObjectClass(env, app->activity->clazz);
     jmethodID java_method = (*env)->GetMethodID(env, ActivityClass,
         (char8*)"showDialogYesNo",
         (char8*)"(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;JJ)V");
     assert( java_method != NULL );

     jstring jTitle = (*env)->NewStringUTF(env, title, strlen(title) );
     jstring jMsg = (*env)->NewStringUTF(env, message, strlen(message) );
     jstring jOK = (*env)->NewStringUTF(env, yes, strlen(yes) );
     jstring jCancel = (*env)->NewStringUTF(env, no, strlen(no) );
     //Note: jlong is 64 bit
     jlong jOnOK = (intptr_t)onOK;
     jlong jOnCancel = (intptr_t)onCancel;
     //invoke UI Dialog in another thread
     (*env)->CallVoidMethod(env, app->activity->clazz , java_method, jTitle, jMsg, jOK, jCancel, jOnOK, jOnCancel);

     (*env)->DeleteLocalRef(env, jTitle);
     (*env)->DeleteLocalRef(env, jMsg);
     (*env)->DeleteLocalRef(env, jOK);
     (*env)->DeleteLocalRef(env, jCancel);
     (*env)->DeleteLocalRef(env, ActivityClass);
 }

native usage sample:

 static void OnExit()
 {
     exit();
 }

 void Android_Confirm_Exit()
 {
     const char* title = "Quit";
     const char* message = "Unsaved progress will be lost.\nAre you sure you want to quit game?";
     const char* yes = "Ok";
     const char* no = "Cancel";
     Android_SystemDialog(title, message, yes, no, &OnExit, NULL);
 }