android - 如何使 LibGDX GLSurfaceView 透明，以便我们可以看到它后面的 Android ImageView？

Question

基本前提是我有 2 个 Android View ...一个填满屏幕的背景 View (在本例中为 ImageView)，以及一个 LibGDX GLSurfaceView在前台，是 LibGDX 应用程序。我想在 LibGDX GLSurfaceView 上打一个洞，这样我就可以看到背景 ImageView 了。即，LibGDX 部分的行为就像一个覆盖层。可悲的是我根本无法让它工作。我剥离了所有代码，只留下了最基本的必需品，希望能展示我正在尝试做的事情。

在完整的应用程序中，它是一个 Android 应用程序，其中背景 View 是一个视频，而前景，由 LibGdx 渲染，是一组视频控件，需要叠加在视频上。

public class MiniClientGDXTestActivity extends AndroidApplication implements ApplicationListener {
    @Bind(R.id.surface)
    FrameLayout uiFrameHolder;

    Stage stage;
    Batch batch;
    Camera camera;
    Viewport viewport;
    ShapeRenderer shapeRenderer;


    private View miniClientView;

    public MiniClientGDXTestActivity() {
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        hideSystemUI(this);

        setContentView(R.layout.miniclientgltest_layout);
        ButterKnife.bind(this);

        AndroidApplicationConfiguration cfg = new AndroidApplicationConfiguration();
        //cfg.useGL20 = false;
        // we need to change the default pixel format - since it does not include an alpha channel
        // we need the alpha channel so the camera preview will be seen behind the GL scene
        cfg.r = 8;
        cfg.g = 8;
        cfg.b = 8;
        cfg.a = 8;

        miniClientView = initializeForView(this, cfg);

        if (graphics.getView() instanceof SurfaceView) {
            SurfaceView glView = (SurfaceView) graphics.getView();
            glView.setBackgroundColor(android.graphics.Color.TRANSPARENT);
            // force alpha channel - I'm not sure we need this as the GL surface is already using alpha channel
            glView.getHolder().setFormat(PixelFormat.TRANSLUCENT);
        }

        uiFrameHolder.addView(miniClientView);
    }

    @Override
    public void create() {
        camera = new OrthographicCamera();
        viewport = new StretchViewport(1920, 1080, camera);
        stage = new Stage(viewport);
        batch = stage.getBatch();
        shapeRenderer = new ShapeRenderer();

        Gdx.graphics.setContinuousRendering(false);
        Gdx.graphics.requestRendering();
    }

    @Override
    public void resize(int width, int height) {
        stage.getViewport().setWorldSize(1920, 1080);
        stage.getViewport().update(width, height, true);
        Gdx.graphics.requestRendering();
    }

    @Override
    public void render() {
        Gdx.gl20.glClearColor(0, 0, 0, 0);
        Gdx.gl20.glClear(GL20.GL_COLOR_BUFFER_BIT | GL20.GL_DEPTH_BUFFER_BIT);

        // draw whatever we have on the stage
        stage.draw();

        // draw red rectangle
        drawRect(10, 10, 1000, 1000);

        // draw a blue box
        fillRect(50, 50, 800, 800);

        // punch a hole in the surface (ie, clear an area) so that we can see the view that is
        // behind this view
        clearRect(200, 200, 1600, 600);
    }

    @Override
    public void pause() {

    }

    @Override
    public void resume() {

    }

    @Override
    public void dispose() {

    }

    public void drawRect(final int x, final int y, final int width, final int height) {
        shapeRenderer.setProjectionMatrix(camera.combined);
        shapeRenderer.begin(ShapeRenderer.ShapeType.Line);
        shapeRenderer.rect(x, y, width, height, Color.RED, Color.RED, Color.RED, Color.RED);
        shapeRenderer.end();
    }

    public void fillRect(final int x, final int y, final int width, final int height) {
        shapeRenderer.setProjectionMatrix(camera.combined);
        shapeRenderer.begin(ShapeRenderer.ShapeType.Filled);
        shapeRenderer.rect(x, y, width, height, Color.BLUE, Color.BLUE, Color.BLUE, Color.BLUE);
        shapeRenderer.end();
    }

    public void clearRect(final int x, final int y, final int width, final int height) {
//                Gdx.gl.glEnable(GL20.GL_BLEND);
//                Gdx.gl.glBlendFunc(GL20.GL_SRC_ALPHA, GL20.GL_ONE_MINUS_SRC_ALPHA);


        shapeRenderer.setProjectionMatrix(camera.combined);
        shapeRenderer.begin(ShapeRenderer.ShapeType.Filled);
        shapeRenderer.setColor(Color.CLEAR);
        shapeRenderer.rect(x, y, width, height);
        shapeRenderer.end();

//                Gdx.gl.glDisable(GL20.GL_BLEND);
    }

}

这是 XML 布局

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:keepScreenOn="true">

    <FrameLayout
        android:visibility="visible"
        android:id="@+id/surface"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">

        <!-- to see if we can see this -->
        <ImageView
            android:layout_width="fill_parent"
            android:layout_height="match_parent" android:scaleType="fitXY" android:src="@drawable/background"/>

        <!-- gdx gets added here -->
    </FrameLayout>


</FrameLayout>

Answer 1

似乎使用 PixelFormat.RGBA_8888 调用 setZOrderOnTop 就可以了。

    if (graphics.getView() instanceof SurfaceView) {
        GLSurfaceView glView = (GLSurfaceView) graphics.getView();
        glView.setZOrderOnTop(true);
        glView.getHolder().setFormat(PixelFormat.RGBA_8888);
    }

现在，当调用 clearRect 方法时，它会在 GLSurfaceView 中打一个洞，以查看下方的 Android View 。