【Android】窗口层级问题

1，概述

在Android世界中，window处在三维世界中，即xyz坐标系。我们所说的z坐标系，简称z序，决定多个窗口在屏幕显示的次序。z序越大，就可以覆盖z序比它小的窗口，符合物理规律。

通过xml创建的窗口，如果不调用系统函数设置，其window.type默认为TYPE_APPLICATION，

在此先贴TYPE类型源码，其值递增；

@ViewDebug.ExportedProperty(mapping = {
                @ViewDebug.IntToString(from = TYPE_BASE_APPLICATION,
                        to = "BASE_APPLICATION"),
                // 应用普通窗口
                @ViewDebug.IntToString(from = TYPE_APPLICATION,
                        to = "APPLICATION"),
                @ViewDebug.IntToString(from = TYPE_APPLICATION_STARTING,
                        to = "APPLICATION_STARTING"),
                @ViewDebug.IntToString(from = TYPE_DRAWN_APPLICATION,
                        to = "DRAWN_APPLICATION"),
                @ViewDebug.IntToString(from = TYPE_APPLICATION_PANEL,
                        to = "APPLICATION_PANEL"),
                @ViewDebug.IntToString(from = TYPE_APPLICATION_MEDIA,
                        to = "APPLICATION_MEDIA"),
                @ViewDebug.IntToString(from = TYPE_APPLICATION_SUB_PANEL,
                        to = "APPLICATION_SUB_PANEL"),
                @ViewDebug.IntToString(from = TYPE_APPLICATION_ABOVE_SUB_PANEL,
                        to = "APPLICATION_ABOVE_SUB_PANEL"),
                @ViewDebug.IntToString(from = TYPE_APPLICATION_ATTACHED_DIALOG,
                        to = "APPLICATION_ATTACHED_DIALOG"),
                @ViewDebug.IntToString(from = TYPE_APPLICATION_MEDIA_OVERLAY,
                        to = "APPLICATION_MEDIA_OVERLAY"),
                @ViewDebug.IntToString(from = TYPE_STATUS_BAR,
                        to = "STATUS_BAR"),
                @ViewDebug.IntToString(from = TYPE_SEARCH_BAR,
                        to = "SEARCH_BAR"),
                @ViewDebug.IntToString(from = TYPE_PHONE,
                        to = "PHONE"),
                @ViewDebug.IntToString(from = TYPE_SYSTEM_ALERT,
                        to = "SYSTEM_ALERT"),
                @ViewDebug.IntToString(from = TYPE_TOAST,
                        to = "TOAST"),
                @ViewDebug.IntToString(from = TYPE_SYSTEM_OVERLAY,
                        to = "SYSTEM_OVERLAY"),
                @ViewDebug.IntToString(from = TYPE_PRIORITY_PHONE,
                        to = "PRIORITY_PHONE"),
                @ViewDebug.IntToString(from = TYPE_SYSTEM_DIALOG,
                        to = "SYSTEM_DIALOG"),
                @ViewDebug.IntToString(from = TYPE_KEYGUARD_DIALOG,
                        to = "KEYGUARD_DIALOG"),
                @ViewDebug.IntToString(from = TYPE_SYSTEM_ERROR,
                        to = "SYSTEM_ERROR"),
                @ViewDebug.IntToString(from = TYPE_INPUT_METHOD,
                        to = "INPUT_METHOD"),
                @ViewDebug.IntToString(from = TYPE_INPUT_METHOD_DIALOG,
                        to = "INPUT_METHOD_DIALOG"),
                @ViewDebug.IntToString(from = TYPE_WALLPAPER,
                        to = "WALLPAPER"),
                @ViewDebug.IntToString(from = TYPE_STATUS_BAR_PANEL,
                        to = "STATUS_BAR_PANEL"),
                @ViewDebug.IntToString(from = TYPE_SECURE_SYSTEM_OVERLAY,
                        to = "SECURE_SYSTEM_OVERLAY"),
                @ViewDebug.IntToString(from = TYPE_DRAG,
                        to = "DRAG"),
                @ViewDebug.IntToString(from = TYPE_STATUS_BAR_SUB_PANEL,
                        to = "STATUS_BAR_SUB_PANEL"),
                @ViewDebug.IntToString(from = TYPE_POINTER,
                        to = "POINTER"),
                @ViewDebug.IntToString(from = TYPE_NAVIGATION_BAR,
                        to = "NAVIGATION_BAR"),
                @ViewDebug.IntToString(from = TYPE_VOLUME_OVERLAY,
                        to = "VOLUME_OVERLAY"),
                @ViewDebug.IntToString(from = TYPE_BOOT_PROGRESS,
                        to = "BOOT_PROGRESS"),
                @ViewDebug.IntToString(from = TYPE_INPUT_CONSUMER,
                        to = "INPUT_CONSUMER"),
                @ViewDebug.IntToString(from = TYPE_NAVIGATION_BAR_PANEL,
                        to = "NAVIGATION_BAR_PANEL"),
                @ViewDebug.IntToString(from = TYPE_DISPLAY_OVERLAY,
                        to = "DISPLAY_OVERLAY"),
                @ViewDebug.IntToString(from = TYPE_MAGNIFICATION_OVERLAY,
                        to = "MAGNIFICATION_OVERLAY"),
                @ViewDebug.IntToString(from = TYPE_PRESENTATION,
                        to = "PRESENTATION"),
                @ViewDebug.IntToString(from = TYPE_PRIVATE_PRESENTATION,
                        to = "PRIVATE_PRESENTATION"),
                @ViewDebug.IntToString(from = TYPE_VOICE_INTERACTION,
                        to = "VOICE_INTERACTION"),
                @ViewDebug.IntToString(from = TYPE_VOICE_INTERACTION_STARTING,
                        to = "VOICE_INTERACTION_STARTING"),
                @ViewDebug.IntToString(from = TYPE_DOCK_DIVIDER,
                        to = "DOCK_DIVIDER"),
                @ViewDebug.IntToString(from = TYPE_QS_DIALOG,
                        to = "QS_DIALOG"),
                @ViewDebug.IntToString(from = TYPE_SCREENSHOT,
                        to = "SCREENSHOT"),
                @ViewDebug.IntToString(from = TYPE_APPLICATION_OVERLAY,
                        to = "APPLICATION_OVERLAY")
        })
        @WindowType
        public int type;

ok，知道这些基本type后，咱们进入WMS.addWindow()查看具体排序逻辑；

2，addWindow（）

在此解释下，addWindow是在创建MainActivity时wms调用的函数，而addView是应用单独拥有的wm添加子窗口的函数，后者添加窗口依据为窗口子序；

public int addWindow(Session session, IWindow client, int seq,
            LayoutParams attrs, int viewVisibility, int displayId, Rect outFrame,
            Rect outContentInsets, Rect outStableInsets,
            DisplayCutout.ParcelableWrapper outDisplayCutout, InputChannel outInputChannel,
            InsetsState outInsetsState, InsetsSourceControl[] outActiveControls,
            int requestUserId) {
           
             //省略参数校验代码
             //......

            //为新窗口创建一个windowState，
            final WindowState win = new WindowState(this, session, client, token, parentWindow,
                    appOp[0], seq, attrs, viewVisibility, session.mUid, userId,
                    session.mCanAddInternalSystemWindow);
            if (win.mDeathRecipient == null) {
                // Client has apparently died, so there is no reason to
                // continue.
                ProtoLog.w(WM_ERROR, "Adding window client %s"
                        + " that is dead, aborting.", client.asBinder());
                return WindowManagerGlobal.ADD_APP_EXITING;
            }

            if (win.getDisplayContent() == null) {
                ProtoLog.w(WM_ERROR, "Adding window to Display that has been removed.");
                return WindowManagerGlobal.ADD_INVALID_DISPLAY;
            }

            final DisplayPolicy displayPolicy = displayContent.getDisplayPolicy();
            displayPolicy.adjustWindowParamsLw(win, win.mAttrs, callingPid, callingUid);

            res = displayPolicy.validateAddingWindowLw(attrs, callingPid, callingUid);
            if (res != WindowManagerGlobal.ADD_OKAY) {
                return res;
            }

            final boolean openInputChannels = (outInputChannel != null
                    && (attrs.inputFeatures & INPUT_FEATURE_NO_INPUT_CHANNEL) == 0);
            if  (openInputChannels) {
                win.openInputChannel(outInputChannel);
            }

            // If adding a toast requires a token for this app we always schedule hiding
            // toast windows to make sure they don't stick around longer then necessary.
            // We hide instead of remove such windows as apps aren't prepared to handle
            // windows being removed under them.
            //
            // If the app is older it can add toasts without a token and hence overlay
            // other apps. To be maximally compatible with these apps we will hide the
            // window after the toast timeout only if the focused window is from another
            // UID, otherwise we allow unlimited duration. When a UID looses focus we
            // schedule hiding all of its toast windows.
            if (type == TYPE_TOAST) {
                if (!displayContent.canAddToastWindowForUid(callingUid)) {
                    ProtoLog.w(WM_ERROR, "Adding more than one toast window for UID at a time.");
                    return WindowManagerGlobal.ADD_DUPLICATE_ADD;
                }
                // Make sure this happens before we moved focus as one can make the
                // toast focusable to force it not being hidden after the timeout.
                // Focusable toasts are always timed out to prevent a focused app to
                // show a focusable toasts while it has focus which will be kept on
                // the screen after the activity goes away.
                if (addToastWindowRequiresToken
                        || (attrs.flags & LayoutParams.FLAG_NOT_FOCUSABLE) == 0
                        || displayContent.mCurrentFocus == null
                        || displayContent.mCurrentFocus.mOwnerUid != callingUid) {
                    mH.sendMessageDelayed(
                            mH.obtainMessage(H.WINDOW_HIDE_TIMEOUT, win),
                            win.mAttrs.hideTimeoutMilliseconds);
                }
            }

            // From now on, no exceptions or errors allowed!

            res = WindowManagerGlobal.ADD_OKAY;

            if (mUseBLAST) {
                res |= WindowManagerGlobal.ADD_FLAG_USE_BLAST;
            }
            if (sEnableTripleBuffering) {
                res |= WindowManagerGlobal.ADD_FLAG_USE_TRIPLE_BUFFERING;
            }

            if (displayContent.mCurrentFocus == null) {
                displayContent.mWinAddedSinceNullFocus.add(win);
            }

            if (excludeWindowTypeFromTapOutTask(type)) {
                displayContent.mTapExcludedWindows.add(win);
            }

            win.attach();
            mWindowMap.put(client.asBinder(), win);
            win.initAppOpsState();

            final boolean suspended = mPmInternal.isPackageSuspended(win.getOwningPackage(),
                    UserHandle.getUserId(win.getOwningUid()));
            win.setHiddenWhileSuspended(suspended);

            final boolean hideSystemAlertWindows = !mHidingNonSystemOverlayWindows.isEmpty();
            win.setForceHideNonSystemOverlayWindowIfNeeded(hideSystemAlertWindows);

            final ActivityRecord tokenActivity = token.asActivityRecord();
            if (type == TYPE_APPLICATION_STARTING && tokenActivity != null) {
                tokenActivity.startingWindow = win;
                ProtoLog.v(WM_DEBUG_STARTING_WINDOW, "addWindow: %s startingWindow=%s",
                        activity, win);
            }

            boolean imMayMove = true;

            win.mToken.addWindow(win);
            displayPolicy.addWindowLw(win, attrs);
            if (type == TYPE_INPUT_METHOD) {
                displayContent.setInputMethodWindowLocked(win);
                imMayMove = false;
            } else if (type == TYPE_INPUT_METHOD_DIALOG) {
                displayContent.computeImeTarget(true /* updateImeTarget */);
                imMayMove = false;
            } else {
                if (type == TYPE_WALLPAPER) {
                    displayContent.mWallpaperController.clearLastWallpaperTimeoutTime();
                    displayContent.pendingLayoutChanges |= FINISH_LAYOUT_REDO_WALLPAPER;
                } else if ((attrs.flags & FLAG_SHOW_WALLPAPER) != 0) {
                    displayContent.pendingLayoutChanges |= FINISH_LAYOUT_REDO_WALLPAPER;
                } else if (displayContent.mWallpaperController.isBelowWallpaperTarget(win)) {
                    // If there is currently a wallpaper being shown, and
                    // the base layer of the new window is below the current
                    // layer of the target window, then adjust the wallpaper.
                    // This is to avoid a new window being placed between the
                    // wallpaper and its target.
                    displayContent.pendingLayoutChanges |= FINISH_LAYOUT_REDO_WALLPAPER;
                }
            }

            final WindowStateAnimator winAnimator = win.mWinAnimator;
            winAnimator.mEnterAnimationPending = true;
            winAnimator.mEnteringAnimation = true;
            // Check if we need to prepare a transition for replacing window first.
            if (activity != null && activity.isVisible()
                    && !prepareWindowReplacementTransition(activity)) {
                // If not, check if need to set up a dummy transition during display freeze
                // so that the unfreeze wait for the apps to draw. This might be needed if
                // the app is relaunching.
                prepareNoneTransitionForRelaunching(activity);
            }

            if (displayPolicy.getLayoutHint(win.mAttrs, token, outFrame, outContentInsets,
                    outStableInsets, outDisplayCutout)) {
                res |= WindowManagerGlobal.ADD_FLAG_ALWAYS_CONSUME_SYSTEM_BARS;
            }
            outInsetsState.set(win.getInsetsState(), win.isClientLocal());

            if (mInTouchMode) {
                res |= WindowManagerGlobal.ADD_FLAG_IN_TOUCH_MODE;
            }
            if (win.mActivityRecord == null || win.mActivityRecord.isClientVisible()) {
                res |= WindowManagerGlobal.ADD_FLAG_APP_VISIBLE;
            }

            displayContent.getInputMonitor().setUpdateInputWindowsNeededLw();

            boolean focusChanged = false;
            if (win.canReceiveKeys()) {
                focusChanged = updateFocusedWindowLocked(UPDATE_FOCUS_WILL_ASSIGN_LAYERS,
                        false /*updateInputWindows*/);
                if (focusChanged) {
                    imMayMove = false;
                }
            }

            if (imMayMove) {
                displayContent.computeImeTarget(true /* updateImeTarget */);
            }

            // Don't do layout here, the window must call
            // relayout to be displayed, so we'll do it there.
            win.getParent().assignChildLayers();

            if (focusChanged) {
                displayContent.getInputMonitor().setInputFocusLw(displayContent.mCurrentFocus,
                        false /*updateInputWindows*/);
            }
            displayContent.getInputMonitor().updateInputWindowsLw(false /*force*/);

            ProtoLog.v(WM_DEBUG_ADD_REMOVE, "addWindow: New client %s"
                    + ": window=%s Callers=%s", client.asBinder(), win, Debug.getCallers(5));

            if (win.isVisibleOrAdding() && displayContent.updateOrientation()) {
                displayContent.sendNewConfiguration();
            }

            getInsetsSourceControls(win, outActiveControls);
        }

        Binder.restoreCallingIdentity(origId);

        return res;
    }

addWindow函数比较长，但结构清晰，先检查参数合法性，然后跟进type解析逻辑，创建一个WindowState，用来保存window状态，windowState构造方法中，为普通窗口赋值z序，mPolicy是WindowManagerPolicy，

// The multiplier here is to reserve space for multiple
// windows in the same type layer.
//主序
mBaseLayer = mPolicy.getWindowLayerLw(this)
        * TYPE_LAYER_MULTIPLIER + TYPE_LAYER_OFFSET;
//子序，默认0，即和父窗口平级
mSubLayer = 0;
            mIsChildWindow = false;
            mLayoutAttached = false;
            mIsImWindow = mAttrs.type == TYPE_INPUT_METHOD
                    || mAttrs.type == TYPE_INPUT_METHOD_DIALOG;
            mIsWallpaper = mAttrs.type == TYPE_WALLPAPER;