我有一个android应用程序，其中在Java端设置了OpenGL上下文，并正在从NDK / C ++端发送图形。这一切似乎都很好。
我希望C ++端能够弹出一个对话框。我实现了一个Java MakeADialog函数，该函数通过env->CallVoidMethod(javaClass, javaMethod);从C端被很好地激发了。Java端的接收函数如下所示：
public static void MakeADialog() {
Log.w("title", "MakeADialog fired!");
}
这是一个单独的类（不是Activity或Runnable）。上面的工作正常，我可以看到我的MakeADialg日志消息。但是，当我尝试创建一个实际的对话框时，我会崩溃。我可以告诉我，当我从C端调用到Java端时，我并没有担心正在运行的“线程”。尝试创建新的线程/对话框时，似乎遇到了麻烦。
我在这里尝试过很多有关创建Runnable，Thread等的建议-但它们似乎总是给我一个可怕的'无法在未调用Looper.prepare（）的线程内创建处理程序的提示。该视图的父级为null。这些方法大多数都围绕着将Activity和Context指针存储为静态，并在进入MakeADialog回调时通过get函数检索它们。
[AlertDialog alertDialog = new AlertDialog.Builder(MyApp.GetMyContext()).create();其中，GetMyContext（）函数只是返回我在应用程序启动期间存储的主要活动创建线程的this指针。
有没有人弹出从NDK端启动的对话框，或者可以指出一些相关文档，这些文档将帮助我了解如何从NDK回调中创建新对话框？
提前感谢！
也许我们可以使用gist中的示例创建一个模式对话框。我怀疑您是从辅助线程中调用它的，因此“它们似乎总是给我一个可怕的'无法在未调用Looper.prepare()的线程内创建处理程序'”或该视图的父级为null。 （另请参见Can't create handler inside thread that has not called Looper.prepare()。）>
基于官方示例Native Activity和the gist code的键代码：
package ss.fang.brickgo;
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.NativeActivity;
import android.content.DialogInterface;
import android.content.pm.ApplicationInfo;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.util.Log;
import android.view.Window;
import android.view.WindowManager;
import java.util.concurrent.Semaphore;
public class GameActivity extends NativeActivity {
// Use a semaphore to create a modal dialog
private final Semaphore semaphore = new Semaphore(0, true);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
// This function will be called from C++ by name and signature
public void showAlert(final String message) {
ApplicationInfo applicationInfo = getApplicationInfo();
final CharSequence appName = getPackageManager().getApplicationLabel(applicationInfo);
this.runOnUiThread(new Runnable() {
public void run() {
AlertDialog.Builder builder = new AlertDialog.Builder(GameActivity.this, AlertDialog.THEME_HOLO_DARK);
builder.setTitle(appName);
builder.setMessage(message);
DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
semaphore.release();
if (DialogInterface.BUTTON_POSITIVE == id) {
GameActivity.this.finish();
}
}
};
builder.setNegativeButton(android.R.string.cancel, listener);
builder.setPositiveButton(android.R.string.ok, listener);
builder.setCancelable(false);
AlertDialog dialog = builder.create();
dialog.show();
}
});
try {
semaphore.acquire();
} catch (InterruptedException e) {
Log.v("GameActivity", "ignored", e);
}
}
protected void showDialog() {
Dialog dialog = new Dialog(this);
dialog.getWindow().requestFeature(Window.FEATURE_NO_TITLE);
dialog.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
// layout to display
dialog.setContentView(R.layout.dialog_layout);
// set color transpartent
dialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
dialog.show();
}
}
void showAlert(struct android_app *state, const char *message);
/** Process the next input event. */
static int32_t engine_handle_input(struct android_app *app, AInputEvent *event) {
auto *engine = (struct engine *) app->userData;
auto type = AInputEvent_getType(event);
if (AINPUT_EVENT_TYPE_MOTION == type) {
engine->animating = 1;
engine->state.x = AMotionEvent_getX(event, 0);
engine->state.y = AMotionEvent_getY(event, 0);
return 1;
} else if (AINPUT_EVENT_TYPE_KEY == type) {
auto action = AKeyEvent_getAction(event);
if (AKEY_EVENT_ACTION_DOWN == action && AKEYCODE_BACK == AKeyEvent_getKeyCode(event)) {
// skip predispatch (all it does is send to the IME)
//if (!AInputQueue_preDispatchEvent(app->inputQueue, event))
//int32_t handled = 0;
//if (app->onInputEvent != NULL) handled = app->onInputEvent(app, event);
//AInputQueue_finishEvent(app->inputQueue, event, handled);
showAlert(app, "Go Back?");
return 1;
}
}
return 0; //not handled
}
void showAlert(struct android_app *state, const char *message) {
JNIEnv *jni = NULL;
state->activity->vm->AttachCurrentThread(&jni, NULL);
jclass clazz = jni->GetObjectClass(state->activity->clazz);
// Get the ID of the method we want to call
// This must match the name and signature from the Java side Signature has to match java
// implementation (second string hints a t a java string parameter)
jmethodID methodID = jni->GetMethodID(clazz, "showAlert", "(Ljava/lang/String;)V");
// Strings passed to the function need to be converted to a java string object
jstring jmessage = jni->NewStringUTF(message);
jni->CallVoidMethod(state->activity->clazz, methodID, jmessage);
// Remember to clean up passed values
jni->DeleteLocalRef(jmessage);
state->activity->vm->DetachCurrentThread();
}