android - 为什么硬件加速在我的 View 上不起作用？

Question

我正在使用 Facebook's Rebound library复制在他们的聊天头实现中看到的有弹性的动画。问题是，大多数时候动画会卡顿。一些图片将更好地解释这一点。这是黄油般流畅的聊天头像动画:

这是我的尝试(注意白色 View 的动画如何跳过几乎所有帧):

偶尔它能顺利运行:

下面是我目前使用的代码(如果您想快速设置，整个项目是 up on Github)。我猜这与我的 View 上未正确启用硬件加速有关。我的 SpringSystem 中有 2 个 Spring，一个用于“气泡”(Android 图标)，另一个用于内容(白色的 View点击气泡时显示)。任何有关如何解决此问题的帮助将不胜感激。谢谢。

AndroidManifest.xml:

    <application android:hardwareAccelerated="true" ...>
        ...
    </application>

AppService.java:

    // the following code is in AppService#onCreate()
    // AppService extends android.app.Service
    // full code at https://github.com/vickychijwani/BubbleNote

    mContent.setLayerType(View.LAYER_TYPE_HARDWARE, null);

    final Spring bubbleSpring = system.createSpring();
    bubbleSpring.setCurrentValue(1.0);
    bubbleSpring.addListener(new SpringListener() {
        @Override
        public void onSpringUpdate(Spring spring) {
            float value = (float) spring.getCurrentValue();
            params.x = (int) (mPos[0] * value);
            params.y = (int) (mPos[1] * value);
            mWindowManager.updateViewLayout(mBubble, params);
            // fire the second animation when this one is about to end
            if (spring.isOvershooting() && contentSpring.isAtRest()) {
                contentSpring.setEndValue(1.0);
            }
        }

        // ...
    });

    final Spring contentSpring = system.createSpring();
    contentSpring.setCurrentValue(0.0);
    contentSpring.addListener(new SpringListener() {
        @Override
        public void onSpringUpdate(Spring spring) {
            // always prints false?!
            Log.d(TAG, "hardware acc = " + mContent.isHardwareAccelerated());
            float value = (float) spring.getCurrentValue();
            // clamping is required to prevent flicker
            float clampedValue = Math.min(Math.max(value, 0.0f), 1.0f);
            mContent.setScaleX(value);
            mContent.setScaleY(value);
            mContent.setAlpha(clampedValue);
        }

        // ...
    });

Answer 1

我已经通过浏览框架源代码弄明白了。

TL;DR:当您手动将 View 附加到 Window 时，将 WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED 添加到布局标志/窗口管理器;在 list 中设置 android:hardwareAccelerated=true 将不起作用。

---

我是 manually attaching my View to the WindowManager (因为我需要在 Service 中创建我的 UI 来模拟聊天头)像这样:

    // code at https://github.com/vickychijwani/BubbleNote/blob/eb708e3910a7279c5490f614a7150009b59bad0b/app/src/main/java/io/github/vickychijwani/bubblenote/BubbleNoteService.java#L54
    mWindowManager = (WindowManager) getSystemService(WINDOW_SERVICE);
    LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
    mBubble = (LinearLayout) inflater.inflate(R.layout.bubble, null, false);
    // ...
    final WindowManager.LayoutParams params = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.TYPE_PHONE,
            WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
            PixelFormat.TRANSLUCENT);
    // ...
    mWindowManager.addView(mBubble, params);

让我们去挖掘...

欢迎使用 Android 框架

我在 View#draw(...) 开始调试, 然后将调用堆栈上升到 ViewRootImpl#draw(boolean) .在这里我遇到了这段代码:

    if (!dirty.isEmpty() || mIsAnimating) {
        if (attachInfo.mHardwareRenderer != null && attachInfo.mHardwareRenderer.isEnabled()) {
            // Draw with hardware renderer.
            mIsAnimating = false;
            mHardwareYOffset = yoff;
            mResizeAlpha = resizeAlpha;

            mCurrentDirty.set(dirty);
            dirty.setEmpty();

            attachInfo.mHardwareRenderer.draw(mView, attachInfo, this,
                    animating ? null : mCurrentDirty);
        } else {
            // If we get here with a disabled & requested hardware renderer, something went
            // wrong (an invalidate posted right before we destroyed the hardware surface
            // for instance) so we should just bail out. Locking the surface with software
            // rendering at this point would lock it forever and prevent hardware renderer
            // from doing its job when it comes back.
            // Before we request a new frame we must however attempt to reinitiliaze the
            // hardware renderer if it's in requested state. This would happen after an
            // eglTerminate() for instance.
            if (attachInfo.mHardwareRenderer != null &&
                    !attachInfo.mHardwareRenderer.isEnabled() &&
                    attachInfo.mHardwareRenderer.isRequested()) {

                try {
                    attachInfo.mHardwareRenderer.initializeIfNeeded(mWidth, mHeight,
                            mHolder.getSurface());
                } catch (OutOfResourcesException e) {
                    handleOutOfResourcesException(e);
                    return;
                }

                mFullRedrawNeeded = true;
                scheduleTraversals();
                return;
            }

            if (!drawSoftware(surface, attachInfo, yoff, scalingRequired, dirty)) {
                return;
            }
        }
    }

以我为例 ViewRootImpl#drawSoftware()被调用，它使用软件渲染器。嗯...这意味着 HardwareRenderer 是 null。所以我去寻找HardwareRenderer的构造点，它在ViewRootImpl#enableHardwareAcceleration(WindowManager.LayoutParams)中。 :

    // Try to enable hardware acceleration if requested
    final boolean hardwareAccelerated =
            (attrs.flags & WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED) != 0;
    if (hardwareAccelerated) {
        // ...
        mAttachInfo.mHardwareRenderer = HardwareRenderer.createGlRenderer(2, translucent);
        // ...
    }

啊哈!这是我们的罪魁祸首!

回到手头的问题

在这种情况下，Android 不会自动为这个 Window 设置 FLAG_HARDWARE_ACCELERATED，即使我已经在显现。所以修复很简单:

    mWindowManager = (WindowManager) getSystemService(WINDOW_SERVICE);
    LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
    mBubble = (LinearLayout) inflater.inflate(R.layout.bubble, null, false);
    // ...
    final WindowManager.LayoutParams params = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.TYPE_PHONE,
            // NOTE
            WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED | WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
            PixelFormat.TRANSLUCENT);
    // ...
    mWindowManager.addView(mBubble, params);

虽然动画还是不如Facebook的流畅。我想知道为什么......(在有人问之前:不，动画期间没有大量日志；是的，我已经尝试过发布版本)