StartingWindow销毁流程 - 安卓R

接着之前的StartingWindow显示流程，现在来介绍StartingWindow的销毁流程。

在View的绘制流程中会调用frameworks/base/core/java/android/view/ViewRootImpl.java的performTraversals方法：

    private void performTraversals() {
        ......
        // Remember if we must report the next draw.
        if ((relayoutResult & WindowManagerGlobal.RELAYOUT_RES_FIRST_TIME) != 0) {
            reportNextDraw();
        }
        ......
    }

    private void reportNextDraw() {
        if (mReportNextDraw == false) {
            drawPending();
        }
        mReportNextDraw = true;
    }

    /**
     * Delay notifying WM of draw finished until
     * a balanced call to pendingDrawFinished.
     */
    void drawPending() {
        mDrawsNeededToReport++;
    }

因为是第一次relayout，因此会调用ViewRootImpl的reportNextDraw方法，将mReportNextDraw设为true。然后在ViewRootImpl的performDraw方法中：

    private void performDraw() {
        ......
        boolean reportNextDraw = mReportNextDraw; // Capture the original value
        if (mAttachInfo.mThreadedRenderer != null && mAttachInfo.mThreadedRenderer.isEnabled()) {
            ArrayList<Runnable> commitCallbacks = mAttachInfo.mTreeObserver
                    .captureFrameCommitCallbacks();
            final boolean needFrameCompleteCallback = mNextDrawUseBLASTSyncTransaction ||
                (commitCallbacks != null && commitCallbacks.size() > 0) ||
                mReportNextDraw;
            usingAsyncReport = mReportNextDraw;
            if (needFrameCompleteCallback) {
                final Handler handler = mAttachInfo.mHandler;
                mAttachInfo.mThreadedRenderer.setFrameCompleteCallback((long frameNr) -> {
                        finishBLASTSync(!mSendNextFrameToWm);
                        handler.postAtFrontOfQueue(() -> {
                            if (reportNextDraw) {
                                // TODO: Use the frame number
                                pendingDrawFinished();
                            }
                            ......
                        });});
            }
        }
        ......
    }

因为mReportNextDraw为true，会调用mAttachInfo.mThreadedRenderer.setFrameCompleteCallback设置一个帧完成时的回调，在回调中会调用ViewRootImpl的pendingDrawFinished方法：

    void pendingDrawFinished() {
        if (mDrawsNeededToReport == 0) {
            throw new RuntimeException("Unbalanced drawPending/pendingDrawFinished calls");
        }
        mDrawsNeededToReport--;
        if (mDrawsNeededToReport == 0) {
            reportDrawFinished();
        }
    }

    private void reportDrawFinished() {
        try {
            mDrawsNeededToReport = 0;
            mWindowSession.finishDrawing(mWindow, mSurfaceChangedTransaction);
        } catch (RemoteException e) {
            // Have fun!
        }
    }

最终会调用了ViewRootImpl的reportDrawFinished方法，在其中通过binder调用了frameworks/base/services/core/java/com/android/server/wm/Session.java的finishDrawing方法：

    @Override
    public void finishDrawing(IWindow window,
            @Nullable SurfaceControl.Transaction postDrawTransaction) {
        if (DEBUG) Slog.v(TAG_WM, "IWindow finishDrawing called for " + window);
        mService.finishDrawingWindow(this, window, postDrawTransaction);
    }

调用了frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java的finishDrawingWindow方法：

    void finishDrawingWindow(Session session, IWindow client,
            @Nullable SurfaceControl.Transaction postDrawTransaction) {
        final long origId = Binder.clearCallingIdentity();
        try {
            synchronized (mGlobalLock) {
                WindowState win = windowForClientLocked(session, client, false);
                ProtoLog.d(WM_DEBUG_ADD_REMOVE, "finishDrawingWindow: %s mDrawState=%s",
                        win, (win != null ? win.mWinAnimator.drawStateToString() : "null"));
                if (win != null && win.finishDrawing(postDrawTransaction)) {
                    if ((win.mAttrs.flags & FLAG_SHOW_WALLPAPER) != 0) {
                        win.getDisplayContent().pendingLayoutChanges |=
                                WindowManagerPolicy.FINISH_LAYOUT_REDO_WALLPAPER;
                    }
                    win.setDisplayLayoutNeeded();
                    mWindowPlacerLocked.requestTraversal();
                }
            }
        } finally {
            Binder.restoreCallingIdentity(origId);
        }
    }

接下来进入窗口布局流程，会调用frameworks/base/services/core/java/com/android/server/wm/DisplayContent.java的mApplySurfaceChangesTransaction方法：

    private final Consumer<WindowState> mApplySurfaceChangesTransaction = w -> {
        ......
            final boolean committed = winAnimator.commitFinishDrawingLocked();
        ......
    };

调用了frameworks/base/services/core/java/com/android/server/wm/WindowStateAnimator.java的commitFinishDrawingLocked方法：

    // This must be called while inside a transaction.
    boolean commitFinishDrawingLocked() {
        if (DEBUG_STARTING_WINDOW_VERBOSE &&
                mWin.mAttrs.type == WindowManager.LayoutParams.TYPE_APPLICATION_STARTING) {
            Slog.i(TAG, "commitFinishDrawingLocked: " + mWin + " cur mDrawState="
                    + drawStateToString());
        }
        if (mDrawState != COMMIT_DRAW_PENDING && mDrawState != READY_TO_SHOW) {
            return false;
        }
        if (DEBUG_ANIM) {
            Slog.i(TAG, "commitFinishDrawingLocked: mDrawState=READY_TO_SHOW " + mSurfaceController);
        }
        mDrawState = READY_TO_SHOW;
        boolean result = false;
        final ActivityRecord activity = mWin.mActivityRecord;
        if (activity == null || activity.canShowWindows()
                || mWin.mAttrs.type == TYPE_APPLICATION_STARTING) {
            result = mWin.performShowLocked();
        }
        return result;
    }

调用了frameworks/base/services/core/java/com/android/server/wm/WindowState.java的performShowLocked方法：

    // This must be called while inside a transaction.
    boolean performShowLocked() {
        ......
        final int drawState = mWinAnimator.mDrawState;
        if ((drawState == HAS_DRAWN || drawState == READY_TO_SHOW) && mActivityRecord != null) {
            if (mAttrs.type != TYPE_APPLICATION_STARTING) {
                mActivityRecord.onFirstWindowDrawn(this, mWinAnimator);
            } else {
                mActivityRecord.onStartingWindowDrawn();
            }
        }
        ......
    }

调用了frameworks/base/services/core/java/com/android/server/wm/ActivityRecord.java的onFirstWindowDrawn方法：

    void onFirstWindowDrawn(WindowState win, WindowStateAnimator winAnimator) {
        firstWindowDrawn = true;

        // We now have a good window to show, remove dead placeholders
        removeDeadWindows();

        if (startingWindow != null) {
            ProtoLog.v(WM_DEBUG_STARTING_WINDOW, "Finish starting %s"
                    + ": first real window is shown, no animation", win.mToken);
            // If this initial window is animating, stop it -- we will do an animation to reveal
            // it from behind the starting window, so there is no need for it to also be doing its
            // own stuff.
            win.cancelAnimation();
        }
        removeStartingWindow();
        updateReportedVisibilityLocked();
    }

调用了ActivityRecord的removeStartingWindow方法：

    void removeStartingWindow() {
        ......
        final WindowManagerPolicy.StartingSurface surface;
        if (mStartingData != null) {
            surface = startingSurface;
            mStartingData = null;
            startingSurface = null;
            startingWindow = null;
            startingDisplayed = false;
            if (surface == null) {
                ProtoLog.v(WM_DEBUG_STARTING_WINDOW,
                        "startingWindow was set but startingSurface==null, couldn't "
                                + "remove");

                return;
            }
        } else {
            ProtoLog.v(WM_DEBUG_STARTING_WINDOW,
                    "Tried to remove starting window but startingWindow was null: %s",
                    this);
            return;
        }

        ProtoLog.v(WM_DEBUG_STARTING_WINDOW, "Schedule remove starting %s startingWindow=%s"
                        + " startingView=%s Callers=%s",
                this, startingWindow, startingSurface, Debug.getCallers(5));


        // Use the same thread to remove the window as we used to add it, as otherwise we end up
        // with things in the view hierarchy being called from different threads.
        mWmService.mAnimationHandler.post(() -> {
            ProtoLog.v(WM_DEBUG_STARTING_WINDOW, "Removing startingView=%s", surface);
            try {
                surface.remove();
            } catch (Exception e) {
                Slog.w(TAG_WM, "Exception when removing starting window", e);
            }
        });
    }

如果之前创建的是TaskSnapshotSurface，则调用了其remove方法：

    @Override
    public void remove() {
        ......
        try {
            ProtoLog.v(WM_DEBUG_STARTING_WINDOW, "Removing snapshot surface");
            mSession.remove(mWindow);
        } catch (RemoteException e) {
            // Local call.
        }
    }

通过mSession.remove将显示窗口移除。

回到ActivityRecord的removeStartingWindow方法中，如果之前创建的是SplashScreenSurface，则调用其remove方法：

    @Override
    public void remove() {
        if (DEBUG_SPLASH_SCREEN) Slog.v(TAG, "Removing splash screen window for " + mAppToken + ": "
                        + this + " Callers=" + Debug.getCallers(4));

        final WindowManager wm = mView.getContext().getSystemService(WindowManager.class);
        wm.removeView(mView);
    }

通过wm.removeView将显示窗口移除。

总结

不管是哪种StartingWindow都是在Activity的窗口绘制了第一帧后消失。