我们可以在 Android 平台上将 Vulkan 与 Java Activity 一起使用吗

Question

目前，似乎所有的 Vulkan 教程和示例都在 Android 平台上使用 NativeActivity。我想知道我们是否可以在 Android 上将 Vulkan 与 Java Activity 一起使用？

Answer 1

假设您有一个 C++ 类，它封装了 Vulkan 绘图逻辑：

// File: AndroidGraphicsApplication.hpp

#include <android/asset_manager.h>
#include <android/native_window.h>
#include "GraphicsApplication.h" // Base class shared with iOS/macOS/...

class AndroidGraphicsApplication : public GraphicsApplication {

public:
    AndroidGraphicsApplication(AAssetManager* assetManager, ANativeWindow* window): GraphicsApplication() {
        mAssetManager = assetManager;
        mWindow = window;
        // ... Vulkan initialisation code.
    }
    ~AndroidGraphicsApplication() {
        // ... Vulkan cleanup code.
    }

    void createSurface() {
       VkAndroidSurfaceCreateInfoKHR surface_info;
       surface_info.sType = VK_STRUCTURE_TYPE_ANDROID_SURFACE_CREATE_INFO_KHR;
       surface_info.pNext = NULL;
       surface_info.flags = 0;
       surface_info.window = mWindow;
       if(vkCreateAndroidSurfaceKHR(instance, &surface_info, NULL, &surface) != VK_SUCCESS) {
          throw std::runtime_error("failed to create window surface!");
       }
    }

    // Used to setup shaders.
    std::vector<char> readFile(const std::string& filename) {
       AAsset* file = AAssetManager_open(mAssetManager, filename.c_str(), AASSET_MODE_BUFFER);
       size_t size = AAsset_getLength(file);
       std::vector<char> data(size);
       AAsset_read(file, data.data(), size);
       AAsset_close(file);
       return data;
    }

    void setSize(uint32_t w, uint32_t h) {
       width = w;
       height = h;
    }

private:
    AAssetManager* mAssetManager;
    ANativeWindow* mWindow;
    uint32_t width;
    uint32_t height;
};

你有 JNI 桥，如下所示：

// File: VulkanAppBridge.cpp

#include <android/log.h>
#include <android/native_window_jni.h>
#include <android/asset_manager_jni.h>
#include "AndroidGraphicsApplication.hpp"

AndroidGraphicsApplication *mApplicationInstance = NULL;

extern "C" {

   JNIEXPORT void JNICALL
   Java_com_mc_demo_vulkan_VulkanAppBridge_nativeCreate(JNIEnv *env, jobject vulkanAppBridge,
         jobject surface, jobject pAssetManager) {
      if (mApplicationInstance) {
         delete mApplicationInstance;
         mApplicationInstance = NULL;
      }
      __android_log_print(ANDROID_LOG_DEBUG, "mc-native-VulkanAppBridge", "create");
      auto window = ANativeWindow_fromSurface(env, surface);
      auto assetManager = AAssetManager_fromJava(env, pAssetManager);
      mApplicationInstance = new AndroidGraphicsApplication(assetManager, window);
   }

   JNIEXPORT void JNICALL
   Java_com_mc_demo_vulkan_VulkanAppBridge_nativeDestroy(JNIEnv *env, jobject vulkanAppBridge) {
      __android_log_print(ANDROID_LOG_DEBUG, "mc-native-VulkanAppBridge", "destroy");
      if (mApplicationInstance) {
         delete mApplicationInstance;
         mApplicationInstance = NULL;
      }
   }

   JNIEXPORT void JNICALL
   Java_com_mc_demo_vulkan_VulkanAppBridge_nativeResize(JNIEnv *env, jobject vulkanAppBridge, jint width, jint height) {
      __android_log_print(ANDROID_LOG_DEBUG, "mc-native-VulkanAppBridge", "resize: %dx%d", width, height);
      if (mApplicationInstance) {
         mApplicationInstance->setSize(width, height);
         mApplicationInstance->isResizeNeeded = true;
      }
   }

   JNIEXPORT void JNICALL
   Java_com_mc_demo_vulkan_VulkanAppBridge_nativeDraw(JNIEnv *env, jobject vulkanAppBridge) {
      __android_log_print(ANDROID_LOG_DEBUG, "mc-native-VulkanAppBridge", "draw");
      if (mApplicationInstance) {
         mApplicationInstance->drawFrame();
      }
   }
}

并且您有 JNI 桥的相应 Java/Kotlin 部分：

// File: VulkanAppBridge.kt

class VulkanAppBridge {

   init {
      System.loadLibrary("myApplication")
   }

   private external fun nativeCreate(surface: Surface, assetManager: AssetManager)
   private external fun nativeDestroy()
   private external fun nativeResize(width: Int, height: Int)
   private external fun nativeDraw()

   fun create(surface: Surface, assetManager: AssetManager) {
      nativeCreate(surface, assetManager)
   }

   fun destroy() {
      nativeDestroy()
   }

   fun resize(width: Int, height: Int) {
      nativeResize(width, height)
   }

   fun draw() {
      nativeDraw()
   }
}

你有一个自定义的子类SurfaceView：

// File: VulkanSurfaceView.kt

class VulkanSurfaceView: SurfaceView, SurfaceHolder.Callback2 {

    private var vulkanApp = VulkanAppBridge()

    constructor(context: Context): super(context) {
    }

    constructor(context: Context, attrs: AttributeSet): super(context, attrs) {
    }

    constructor(context: Context, attrs: AttributeSet, defStyle: Int): super(context, attrs, defStyle) {
    }

    constructor(context: Context, attrs: AttributeSet, defStyle: Int, defStyleRes: Int): super(context, attrs, defStyle, defStyleRes) {
    }

    init {
        alpha = 1F
        holder.addCallback(this)
    }

    // ...
    // Implementation code similar to one in GLSurfaceView is skipped.
    // See: https://android.googlesource.com/platform/frameworks/base/+/master/opengl/java/android/opengl/GLSurfaceView.java
    // ...

    override fun surfaceChanged(holder: SurfaceHolder?, format: Int, width: Int, height: Int) {
        vulkanApp.resize(width, height)
    }

    override fun surfaceDestroyed(holder: SurfaceHolder?) {
        vulkanApp.destroy()
    }

    override fun surfaceCreated(holder: SurfaceHolder?) {
        holder?.let { h ->
            vulkanApp.create(h.surface, resources.assets)
        }
    }

    override fun surfaceRedrawNeeded(holder: SurfaceHolder?) {
        vulkanApp.draw()
    }
}

然后，您可以使用VulkanSurfaceView具有自定义大小的自定义内部布局以及其他视图：

// File: VulkanAppBridge.kt

class VulkanAppBridge {

   init {
      System.loadLibrary("myApplication")
   }

   private external fun nativeCreate(surface: Surface, assetManager: AssetManager)
   private external fun nativeDestroy()
   private external fun nativeResize(width: Int, height: Int)
   private external fun nativeDraw()

   fun create(surface: Surface, assetManager: AssetManager) {
      nativeCreate(surface, assetManager)
   }

   fun destroy() {
      nativeDestroy()
   }

   fun resize(width: Int, height: Int) {
      nativeResize(width, height)
   }

   fun draw() {
      nativeDraw()
   }
}

结果：

这是“Vulkan 案例研究”的链接，其中包含 Android 使用示例：https : //www.khronos.org/assets/uploads/developers/library/2016-vulkan-devu-seoul/2-Vulkan-Case-Study。 pdf

Answer 2

是的，您可以将 Vulkan 与您自己的 Activity 子类一起使用。由于 Android 没有 Vulkan 的 Java 语言绑定，因此您需要使用 JNI 或第三方 Java Vulkan 库（它只是为您执行 JNI）。

您的 View 层次结构需要包含一个SurfaceView，当您获得 Surfaceholder.Callback#surfaceChanged 回调时，您可以获得 Surface。如果您自己执行 JNI，则可以调用ANativeWindow_fromSurface从 Surface 获取 ANativeWindow，并使用它来创建 VkSurfaceKHR/VkSwapchainKHR。

需要注意的一件事是避免在调用 VkAcquireNextImageKHR 时阻塞主 UI 线程。要么进行安排，以便仅在它不会长时间阻塞时调用它，要么将帧循环放在单独的线程上。