Android外部imgui绘制(一)

前言

上篇文章通过 Magisk Hook eglSwapBuffers 实现绘制，但是某些使用 ue4 引擎制作的游戏却并不能绘制成功.-_-
那就只能用悬浮窗的办法来绘制一个悬浮的 imgui.

方案

注意到，imgui 的绘制基本上都借助了 opengl 函数。而且 imgui 也有官方的安卓版本示例.
https://github.com/ocornut/imgui
基本上可以确定要用 ndk 开发.

其实 opengl 在 ndk 的官方示例里也有.
https://github.com/android/ndk-samples

gles3jni 是 opengl3 的
hello-gl2 是 opengl2 的
选哪个都可以
我选的是 hello-gl2.

然后把 imgui 的代码 clone 下来丢到 cpp 文件夹里面

如图所示.

然后打开 GL2JNIView.java , 设置透明为 true

public GL2JNIView(Context context) {
        super(context);
        init(true, 0, 0);
    }

只需要修改 Renderer 类的 onDrawFrame,onSurfaceChanged,onSurfaceCreated 就行.

onSurfaceCreated

在 onSurfaceCreated 里完成 imgui 的初始化即可，没啥特别的。把 imgui 初始化的代码 copy 过来就行

public void onSurfaceCreated(GL10 gl, EGLConfig config) {
            init_ImGui(this.holder.getSurface());
        }

extern "C"
JNIEXPORT void JNICALL
Java_com_shocker_nativeactivity_GL2JNIView_init_1ImGui(JNIEnv *env, jclass clazz, jobject surface) {
    // TODO: implement init_ImGui()
    ANativeWindow* w = ANativeWindow_fromSurface(env, (jobject)surface);
    ImGuiInit(w);
    ANativeWindow_release(w);
}

void ImGuiInit(ANativeWindow *pWindow) {
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO &io = ImGui::GetIO();
    // Disable loading/saving of .ini file from disk.
    // FIXME: Consider using LoadIniSettingsFromMemory() / SaveIniSettingsToMemory() to save in appropriate location for Android.
    io.IniFilename = NULL;
    // Setup Dear ImGui style
    ImGui::StyleColorsLight();
    //ImGui::StyleColorsClassic();
    // Setup Platform/Renderer backends

    ImGui::SetColorEditOptions(ImGuiColorEditFlags_PickerHueWheel);

    io.Fonts->AddFontFromMemoryTTF((void *)font_data, font_size, 24.0f, NULL, io.Fonts->GetGlyphRangesChineseFull());

    ImGui_ImplAndroid_Init(pWindow);
    ImGui_ImplOpenGL3_Init("#version 300 es");
}

onSurfaceChanged

这个函数一般会在屏幕旋转的时候调用，这里重新设置下 imgui 的大小就行

public void onSurfaceChanged(GL10 gl, int width, int height) {
            update_ImGui(width,height);
        }

extern "C"
JNIEXPORT void JNICALL
Java_com_shocker_nativeactivity_GL2JNIView_update_1ImGui(JNIEnv *env, jclass clazz, jint width,
                                                         jint height) {
    // TODO: implement update_ImGui()
    glViewport(0, 0, width, height);
    ImGui::GetIO().DisplaySize = ImVec2((float)width, (float)height);
}

onDrawFrame

这个函数就是 imgui 的绘制函数了。这里也基本上可以照搬 imgui 的 tick 函数.

public void onDrawFrame(GL10 gl) {
    step();
}

extern "C"
JNIEXPORT void JNICALL
Java_com_shocker_nativeactivity_GL2JNIView_step(JNIEnv *env, jclass clazz) {
    //....处理触摸事件
    tick();
}

void tick()
{
    ImGuiIO& io = ImGui::GetIO();
    if (g_EglDisplay == EGL_NO_DISPLAY)
        return;

    // Our state
    static bool show_demo_window = true;
    static bool show_another_window = false;
    static ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

    // Poll Unicode characters via JNI
    // FIXME: do not call this every frame because of JNI overhead
    PollUnicodeChars();

    // Open on-screen (soft) input if requested by Dear ImGui
    static bool WantTextInputLast = false;
    if (io.WantTextInput && !WantTextInputLast)
        ShowSoftKeyboardInput();
    WantTextInputLast = io.WantTextInput;

    // Start the Dear ImGui frame
    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplAndroid_NewFrame();
    ImGui::NewFrame();

    // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
    if (show_demo_window)
        ImGui::ShowDemoWindow(&show_demo_window);

    // 2. Show a simple window that we create ourselves. We use a Begin/End pair to created a named window.
    {
        static float f = 0.0f;
        static int counter = 0;

        ImGui::Begin("Hello, world!"); // Create a window called "Hello, world!" and append into it.

        ImGui::Text("This is some useful text.");               // Display some text (you can use a format strings too)
        ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
        ImGui::Checkbox("Another Window", &show_another_window);

        ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
        ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color

        if (ImGui::Button("Button"))                            // Buttons return true when clicked (most widgets return true when edited/activated)
            counter++;
        ImGui::SameLine();
        ImGui::Text("counter = %d", counter);

        ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
        ImGui::End();
    }

    // 3. Show another simple window.
    if (show_another_window)
    {
        ImGui::Begin("Another Window", &show_another_window);   // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
        ImGui::Text("Hello from another window!");
        if (ImGui::Button("Close Me"))
            show_another_window = false;
        ImGui::End();
    }

    // Rendering
    ImGui::Render();
    glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
    glClearColor(0, 0, 0, 0);
    glClear(GL_COLOR_BUFFER_BIT);
    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
    // eglSwapBuffers(g_EglDisplay, g_EglSurface);
}

不过这里貌似不需要调用 eglSwapBuffers 函数.

悬浮窗

没啥好说的，直接参考我之前的 github 或者 52 论坛都行
https://github.com/PShocker/Android_float_view_draw
https://www.52pojie.cn/thread-1584152-1-1.html

注意

在我的安卓 12 的版本上，如果要添加悬浮窗必须要添加悬浮窗权限。先判断是否有权限然后再申请

if (android.os.Build.VERSION.SDK_INT >= 23 && !Settings.canDrawOverlays(this)) {
    Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:" + getPackageName()));
    startActivityForResult(intent, 0);
}