前言

DisplayContent 用于管理屏幕，一塊DisplayContent 對象實例代表一個屏幕設(shè)備，這樣有多個屏幕的設(shè)備就可以創(chuàng)建多個DisplayContent 對象，雖然多數(shù)設(shè)備只有一個顯示屏，但它們同樣可以創(chuàng)建多個 DisplayContent 對象，如投屏的時候，可以創(chuàng)建一個虛擬的DisplayContent。

一、DisplayContent 的創(chuàng)建

1、DisplayContent對象實例的創(chuàng)建最早是在SystemServer中被觸發(fā)的。

frameworks/base/services/java/com/android/server/SystemServer.java

public final class SystemServer implements Dumpable {

    private ActivityManagerService mActivityManagerService;

    private void startOtherServices(@NonNull TimingsTraceAndSlog t) {
    		...代碼省略...
            t.traceBegin("SetWindowManagerService");
            mActivityManagerService.setWindowManager(wm);//創(chuàng)建屏幕設(shè)備對象
            t.traceEnd();
            ...代碼省略...
    }
}

該方法會調(diào)用ActivityManagerService的setWindowManager方法。

2、ActivityManagerService的setWindowManager方法如下所示。

frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

public class ActivityManagerService extends IActivityManager.Stub
        implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback, ActivityManagerGlobalLock {
    
    public WindowManagerService mWindowManager;
    public ActivityTaskManagerService mActivityTaskManager;
    
    public void setWindowManager(WindowManagerService wm) {
        synchronized (this) {
            mWindowManager = wm;
            mWmInternal = LocalServices.getService(WindowManagerInternal.class);
            mActivityTaskManager.setWindowManager(wm);//創(chuàng)建屏幕設(shè)備對象
        }
    }
}

該方法會調(diào)用ActivityTaskManagerService的setWindowManager方法。

3、ActivityTaskManagerService的setWindowManager方法如下所示。

frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java

public class ActivityTaskManagerService extends IActivityTaskManager.Stub {

    RootWindowContainer mRootWindowContainer;

    public void setWindowManager(WindowManagerService wm) {
        synchronized (mGlobalLock) {
            mWindowManager = wm;
            mRootWindowContainer = wm.mRoot;//獲取WindowManagerService的RootWindowContainer對象
            mWindowOrganizerController.setWindowManager(wm);
            mTempConfig.setToDefaults();
            mTempConfig.setLocales(LocaleList.getDefault());
            mConfigurationSeq = mTempConfig.seq = 1;
            mRootWindowContainer.onConfigurationChanged(mTempConfig);
            mLockTaskController.setWindowManager(wm);
            mTaskSupervisor.setWindowManager(wm);
            mRootWindowContainer.setWindowManager(wm);//創(chuàng)建屏幕設(shè)備對象
        }
    }
 }

該方法會繼續(xù)調(diào)用RootWindowContainer的setWindowManager方法。

4、DisplayContent對象實例就是在RootWindowContainer的setWindowManager方法中創(chuàng)建的。

frameworks/base/services/core/java/com/android/server/wm/RootWindowContainer.java

class RootWindowContainer extends WindowContainer<DisplayContent>
        implements DisplayManager.DisplayListener {

    DisplayManager mDisplayManager;
    /** Reference to default display so we can quickly look it up. */
    private DisplayContent mDefaultDisplay;

    void setWindowManager(WindowManagerService wm) {
        mWindowManager = wm;
        mDisplayManager = mService.mContext.getSystemService(DisplayManager.class);
        mDisplayManager.registerDisplayListener(this, mService.mUiHandler);
        mDisplayManagerInternal = LocalServices.getService(DisplayManagerInternal.class);

        final Display[] displays = mDisplayManager.getDisplays();//通過DisplayManager獲取屏幕設(shè)備信息
        for (int displayNdx = 0; displayNdx < displays.length; ++displayNdx) {//遍歷屏幕設(shè)備，為每個設(shè)備創(chuàng)建DisplayContent對象
            final Display display = displays[displayNdx];
            final DisplayContent displayContent = new DisplayContent(display, this);//創(chuàng)建屏幕對象DisplayContent實例
            addChild(displayContent, POSITION_BOTTOM);
            if (displayContent.mDisplayId == DEFAULT_DISPLAY) {
                mDefaultDisplay = displayContent;
            }
        }
        calculateDefaultMinimalSizeOfResizeableTasks();

        final TaskDisplayArea defaultTaskDisplayArea = getDefaultTaskDisplayArea();
        defaultTaskDisplayArea.getOrCreateRootHomeTask(ON_TOP);
        positionChildAt(POSITION_TOP, defaultTaskDisplayArea.mDisplayContent,
                false /* includingParents */);
    }
    
    //添加新創(chuàng)建的DisplayContent屏幕設(shè)備對象，將其存儲到父類屬性mChildren集合中
    void addChild(E child, int index) {
        if (!child.mReparenting && child.getParent() != null) {
            throw new IllegalArgumentException("addChild: container=" + child.getName()
                    + " is already a child of container=" + child.getParent().getName()
                    + " can't add to container=" + getName()
                    + "\n callers=" + Debug.getCallers(15, "\n"));
        }

        if ((index < 0 && index != POSITION_BOTTOM)
                || (index > mChildren.size() && index != POSITION_TOP)) {
            throw new IllegalArgumentException("addChild: invalid position=" + index
                    + ", children number=" + mChildren.size());
        }

        if (index == POSITION_TOP) {
            index = mChildren.size();
        } else if (index == POSITION_BOTTOM) {
            index = 0;
        }
		//將DisplayContent屏幕設(shè)備對象存儲到父類屬性mChildren集合中
        mChildren.add(index, child);

        // Set the parent after we've actually added a child in case a subclass depends on this.
        child.setParent(this);
    }
}

frameworks/base/services/core/java/com/android/server/wm/WindowContainer.java

class WindowContainer<E extends WindowContainer> extends ConfigurationContainer<E>
        implements Comparable<WindowContainer>, Animatable, SurfaceFreezer.Freezable {
	protected final WindowList<E> mChildren = new WindowList<E>();
}

1）首先通過DisplayManager獲取當前存在的屏幕設(shè)備信息數(shù)組，然后遍歷該數(shù)組為每個屏幕設(shè)備創(chuàng)建對應(yīng)的DisplayContent對象實例。
2）調(diào)用addChild方法依次將創(chuàng)建的DisplayContent對象實例存儲到父類的mChildren集合中。

二、DisplayContent類定義

frameworks/base/services/core/java/com/android/server/wm/DisplayContent.java文章來源地址http://www.zghlxwxcb.cn/news/detail-467817.html

class DisplayContent extends RootDisplayArea implements WindowManagerPolicy.DisplayContentInfo {

    /**
     * Create new {@link DisplayContent} instance, add itself to the root window container and
     * initialize direct children.
     * @param display May not be null.
     * @param root {@link RootWindowContainer}
     */
    DisplayContent(Display display, RootWindowContainer root) {
        super(root.mWindowManager, "DisplayContent", FEATURE_ROOT);
        if (mWmService.mRoot.getDisplayContent(display.getDisplayId()) != null) {
            throw new IllegalArgumentException("Display with ID=" + display.getDisplayId()
                    + " already exists="
                    + mWmService.mRoot.getDisplayContent(display.getDisplayId())
                    + " new=" + display);
        }

        mRootWindowContainer = root;
        mAtmService = mWmService.mAtmService;
        mDisplay = display;
        mDisplayId = display.getDisplayId();
        mCurrentUniqueDisplayId = display.getUniqueId();
        mOffTokenAcquirer = mRootWindowContainer.mDisplayOffTokenAcquirer;
        mWallpaperController = new WallpaperController(mWmService, this);
        display.getDisplayInfo(mDisplayInfo);
        display.getMetrics(mDisplayMetrics);
        mSystemGestureExclusionLimit = mWmService.mConstants.mSystemGestureExclusionLimitDp
                * mDisplayMetrics.densityDpi / DENSITY_DEFAULT;
        isDefaultDisplay = mDisplayId == DEFAULT_DISPLAY;
        mInsetsStateController = new InsetsStateController(this);
        mDisplayFrames = new DisplayFrames(mDisplayId, mInsetsStateController.getRawInsetsState(),
                mDisplayInfo, calculateDisplayCutoutForRotation(mDisplayInfo.rotation),
                calculateRoundedCornersForRotation(mDisplayInfo.rotation),
                calculatePrivacyIndicatorBoundsForRotation(mDisplayInfo.rotation));
        initializeDisplayBaseInfo();

        mAppTransition = new AppTransition(mWmService.mContext, mWmService, this);
        mAppTransition.registerListenerLocked(mWmService.mActivityManagerAppTransitionNotifier);
        mAppTransition.registerListenerLocked(mFixedRotationTransitionListener);
        mAppTransitionController = new AppTransitionController(mWmService, this);
        mUnknownAppVisibilityController = new UnknownAppVisibilityController(mWmService, this);

        final InputChannel inputChannel = mWmService.mInputManager.monitorInput(
                "PointerEventDispatcher" + mDisplayId, mDisplayId);
        mPointerEventDispatcher = new PointerEventDispatcher(inputChannel, this);

        // Tap Listeners are supported for:
        // 1. All physical displays (multi-display).
        // 2. VirtualDisplays on VR, AA (and everything else).
        mTapDetector = new TaskTapPointerEventListener(mWmService, this);
        registerPointerEventListener(mTapDetector);
        registerPointerEventListener(mWmService.mMousePositionTracker);
        if (mWmService.mAtmService.getRecentTasks() != null) {
            registerPointerEventListener(
                    mWmService.mAtmService.getRecentTasks().getInputListener());
        }

        mDisplayPolicy = new DisplayPolicy(mWmService, this);
        mDisplayRotation = new DisplayRotation(mWmService, this);
        mCloseToSquareMaxAspectRatio = mWmService.mContext.getResources().getFloat(
                com.android.internal.R.dimen.config_closeToSquareDisplayMaxAspectRatio);
        if (isDefaultDisplay) {
            // The policy may be invoked right after here, so it requires the necessary default
            // fields of this display content.
            mWmService.mPolicy.setDefaultDisplay(this);
        }
        if (mWmService.mDisplayReady) {
            mDisplayPolicy.onConfigurationChanged();
        }
        if (mWmService.mSystemReady) {
            mDisplayPolicy.systemReady();
        }
        mWindowCornerRadius = mDisplayPolicy.getWindowCornerRadius();
        mDividerControllerLocked = new DockedTaskDividerController(this);
        mPinnedTaskController = new PinnedTaskController(mWmService, this);

        final Transaction pendingTransaction = getPendingTransaction();
        configureSurfaces(pendingTransaction);
        pendingTransaction.apply();

        // Sets the display content for the children.
        onDisplayChanged(this);
        updateDisplayAreaOrganizers();

        mInputMonitor = new InputMonitor(mWmService, this);
        mInsetsPolicy = new InsetsPolicy(mInsetsStateController, this);

        if (DEBUG_DISPLAY) Slog.v(TAG_WM, "Creating display=" + display);

        mWmService.mDisplayWindowSettings.applySettingsToDisplayLocked(this);
    }
}

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