Android alert display functionality using JNI

android/examples/triangle/build.gradle

@@ -1,9 +1,10 @@
 apply plugin: 'com.android.application'
+apply from: '../gradle/outputfilename.gradle'
 
 android {
     compileSdkVersion 26
     defaultConfig {
-        applicationId "de.saschawillems.vulkanTriangle"
+        applicationId "de.saschawillems.VulkanTriangle"
         minSdkVersion 19
         targetSdkVersion 26
         versionCode 1

android/examples/triangle/src/main/java/de/saschawillems/vulkanSample/VulkanActivity.java

@@ -5,10 +5,18 @@
  */
 package de.saschawillems.vulkanSample;
 
+import android.app.AlertDialog;
 import android.app.NativeActivity;
+import android.content.DialogInterface;
+import android.content.pm.ApplicationInfo;
 import android.os.Bundle;
 
+import java.util.concurrent.Semaphore;
+
 public class VulkanActivity extends NativeActivity {
+
+    VulkanActivity _activity;
+
     static {
         // Load native library
         System.loadLibrary("native-lib");
@@ -16,5 +24,36 @@ public class VulkanActivity extends NativeActivity {
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
+        _activity = this;
+    }
+
+    // Use a semaphore to create a modal dialog
+
+    private final Semaphore semaphore = new Semaphore(0, true);
+
+    public void showAlert(final String message)
+    {
+        ApplicationInfo applicationInfo = _activity.getApplicationInfo();
+        final String applicationName = applicationInfo.nonLocalizedLabel.toString();
+
+        this.runOnUiThread(new Runnable() {
+           public void run() {
+               AlertDialog.Builder builder = new AlertDialog.Builder(_activity, AlertDialog.THEME_HOLO_DARK);
+               builder.setTitle(applicationName);
+               builder.setMessage(message);
+               builder.setPositiveButton("Close", new DialogInterface.OnClickListener() {
+                   public void onClick(DialogInterface dialog, int id) {
+                       semaphore.release();
+                   }
+               });
+               builder.setCancelable(false);
+               AlertDialog dialog = builder.create();
+               dialog.show();
+           }
+        });
+        try {
+            semaphore.acquire();
+        }
+        catch (InterruptedException e) { }
     }
 }

base/VulkanAndroid.cpp

@@ -11,6 +11,7 @@
 #if defined(__ANDROID__)
 	#include <android/log.h>
 	#include <dlfcn.h>
+	#include <android/native_window_jni.h>
 
 android_app* androidApp;
 
@@ -292,6 +293,23 @@ namespace vks
 			vks::android::screenDensity = AConfiguration_getDensity(config);
 			AConfiguration_delete(config);
 		}
+
+		// Displays a native alert dialog using JNI
+		void showAlert(const char* message) {
+			JNIEnv* jni;
+			androidApp->activity->vm->AttachCurrentThread(&jni, NULL);
+
+			jstring jmessage = jni->NewStringUTF(message);
+
+			jclass clazz = jni->GetObjectClass(androidApp->activity->clazz);
+			// Signature has to match java implementation (arguments)
+			jmethodID methodID = jni->GetMethodID(clazz, "showAlert", "(Ljava/lang/String;)V");
+			jni->CallVoidMethod(androidApp->activity->clazz, methodID, jmessage);
+			jni->DeleteLocalRef(jmessage);
+
+			androidApp->activity->vm->DetachCurrentThread();
+			return;
+		}
 	}
 }
 

base/VulkanAndroid.h

@@ -26,6 +26,7 @@
 #include <android_native_app_glue.h>
 #include <android/configuration.h>
 #include <memory>
+#include <string>
 
 // Missing from the NDK
 namespace std
@@ -169,6 +170,7 @@ namespace vks
 		void loadVulkanFunctions(VkInstance instance);
 		void freeVulkanLibrary();
 		void getDeviceConfig();
+		void showAlert(const char* message);
 	}
 }
 

base/VulkanTools.cpp

@@ -270,6 +270,7 @@ namespace vks
 			}
 #elif defined(__ANDROID__)
             LOGE("Fatal error: %s", message.c_str());
+			vks::android::showAlert(message.c_str());
 #endif
 			std::cerr << message << "\n";
 			exit(exitCode);