【DisplayContext】

/**
 * Window that is currently interacting with the user. This window is responsible for receiving
 * key events and pointer events from the user.
 */
WindowState mCurrentFocus = null;

/**
 * The foreground app of this display. Windows below this app cannot be the focused window. If
 * the user taps on the area outside of the task of the focused app, we will notify AM about the
 * new task the user wants to interact with.
 */
ActivityRecord mFocusedApp = null;

设置焦点应用DC.setFocusedApp

    /**
     * Set the new focused app to this display.
     *
     * @param newFocus the new focused {@link ActivityRecord}.
     * @return true if the focused app is changed.
     */
    boolean setFocusedApp(ActivityRecord newFocus) {
        if (newFocus != null) {
            final DisplayContent appDisplay = newFocus.getDisplayContent();
            if (appDisplay != this) {
                throw new IllegalStateException(newFocus + " is not on " + getName()
                        + " but " + ((appDisplay != null) ? appDisplay.getName() : "none"));
            }

            // Called even if the focused app is not changed in case the app is moved to a different
            // TaskDisplayArea.
            onLastFocusedTaskDisplayAreaChanged(newFocus.getDisplayArea());
        }
        if (mFocusedApp == newFocus) {
            return false;
        }
        ProtoLog.i(WM_DEBUG_FOCUS_LIGHT, "setFocusedApp %s displayId=%d Callers=%s",
                newFocus, getDisplayId(), Debug.getCallers(4));
        final Task oldTask = mFocusedApp != null ? mFocusedApp.getTask() : null;
        final Task newTask = newFocus != null ? newFocus.getTask() : null;
//1. 设置焦点应用
        mFocusedApp = newFocus;
        if (oldTask != newTask) {
            if (oldTask != null) oldTask.onAppFocusChanged(false);
            if (newTask != null) newTask.onAppFocusChanged(true);
        }
//2. 更新input的焦点应用
        getInputMonitor().setFocusedAppLw(newFocus);
        updateTouchExcludeRegion();
        return true;
    }

设置焦点窗口

    boolean updateFocusedWindowLocked(int mode, boolean updateInputWindows) {
        Trace.traceBegin(TRACE_TAG_WINDOW_MANAGER, "wmUpdateFocus");
        boolean changed = mRoot.updateFocusedWindowLocked(mode, updateInputWindows);
        Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
        return changed;
    }

    /**
     * Update the focused window and make some adjustments if the focus has changed.
     *
     * @param mode Indicates the situation we are in. Possible modes are:
     *             {@link WindowManagerService#UPDATE_FOCUS_NORMAL},
     *             {@link WindowManagerService#UPDATE_FOCUS_PLACING_SURFACES},
     *             {@link WindowManagerService#UPDATE_FOCUS_WILL_PLACE_SURFACES},
     *             {@link WindowManagerService#UPDATE_FOCUS_REMOVING_FOCUS}
     * @param updateInputWindows Whether to sync the window information to the input module.
     * @param topFocusedDisplayId Display id of current top focused display.
     * @return {@code true} if the focused window has changed.
     */
    boolean updateFocusedWindowLocked(int mode, boolean updateInputWindows,
            int topFocusedDisplayId) {

[inputmonitor.java]

    /**
     * Immediately update the input transaction and merge into the passing Transaction that could be
     * collected and applied later.
     */
    void updateInputWindowsImmediately(SurfaceControl.Transaction t) {
        mHandler.removeCallbacks(mUpdateInputWindows);
        mUpdateInputWindowsImmediately = true;
        mUpdateInputWindows.run();
        mUpdateInputWindowsImmediately = false;
        t.merge(mInputTransaction);
    }