[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) < 0 )
        (*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(0);
}

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