先来看一下android支持的屏幕方向
我们平时接触的：
横向，纵向，默认
来看一看Android的描述
ActivityInfo.java

    /**
     * Internal constant used to indicate that the app didn't set a specific orientation value.
     * Different from {@link #SCREEN_ORIENTATION_UNSPECIFIED} below as the app can set its
     * orientation to {@link #SCREEN_ORIENTATION_UNSPECIFIED} while this means that the app didn't
     * set anything. The system will mostly treat this similar to
     * {@link #SCREEN_ORIENTATION_UNSPECIFIED}.
     * @hide
     */
    public static final int SCREEN_ORIENTATION_UNSET = -2;
    /**
     * Constant corresponding to <code>unspecified</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_UNSPECIFIED = -1;
    /**
     * Constant corresponding to <code>landscape</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_LANDSCAPE = 0;
    /**
     * Constant corresponding to <code>portrait</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_PORTRAIT = 1;
    /**
     * Constant corresponding to <code>user</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_USER = 2;
    /**
     * Constant corresponding to <code>behind</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_BEHIND = 3;
    /**
     * Constant corresponding to <code>sensor</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_SENSOR = 4;

    /**
     * Constant corresponding to <code>nosensor</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_NOSENSOR = 5;

    /**
     * Constant corresponding to <code>sensorLandscape</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_SENSOR_LANDSCAPE = 6;

    /**
     * Constant corresponding to <code>sensorPortrait</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_SENSOR_PORTRAIT = 7;

    /**
     * Constant corresponding to <code>reverseLandscape</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_REVERSE_LANDSCAPE = 8;

    /**
     * Constant corresponding to <code>reversePortrait</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_REVERSE_PORTRAIT = 9;

    /**
     * Constant corresponding to <code>fullSensor</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_FULL_SENSOR = 10;

    /**
     * Constant corresponding to <code>userLandscape</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_USER_LANDSCAPE = 11;

    /**
     * Constant corresponding to <code>userPortrait</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_USER_PORTRAIT = 12;

    /**
     * Constant corresponding to <code>fullUser</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_FULL_USER = 13;

    /**
     * Constant corresponding to <code>locked</code> in
     * the {@link android.R.attr#screenOrientation} attribute.
     */
    public static final int SCREEN_ORIENTATION_LOCKED = 14;

总体流程图：

getoritation.jpg

public int relayoutWindow(Session session, IWindow client, int seq, LayoutParams attrs,
            int requestedWidth, int requestedHeight, int viewVisibility, int flags,
            long frameNumber, Rect outFrame, Rect outOverscanInsets, Rect outContentInsets,
            Rect outVisibleInsets, Rect outStableInsets, Rect outOutsets, Rect outBackdropFrame,
            DisplayCutout.ParcelableWrapper outCutout, MergedConfiguration mergedConfiguration,
            SurfaceControl outSurfaceControl, InsetsState outInsetsState) {
            Trace.traceBegin(TRACE_TAG_WINDOW_MANAGER,
                    "relayoutWindow: updateOrientationFromAppTokens");
//更新window方向
            configChanged = displayContent.updateOrientationFromAppTokens();
            Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
}

    private boolean updateOrientationFromAppTokens(boolean forceUpdate) {
//getOrientation
        final int req = getOrientation();
        if (req != mLastOrientation || forceUpdate) {
            mLastOrientation = req;
            mDisplayRotation.setCurrentOrientation(req);
            return updateRotationUnchecked(forceUpdate);
        }
        return false;
    }

这里决定了当前window方向

        int getOrientation() {
//是否分屏 是否画中画
            if (isStackVisible(WINDOWING_MODE_SPLIT_SCREEN_PRIMARY)
                    || isStackVisible(WINDOWING_MODE_FREEFORM)) {
                // Apps and their containers are not allowed to specify an orientation while the
                // docked or freeform stack is visible...except for the home stack if the docked
                // stack is minimized and it actually set something and the bounds is different from
                // the display.
                if (mHomeStack != null && mHomeStack.isVisible()
                        && mDividerControllerLocked.isMinimizedDock()
                        && !(mDividerControllerLocked.isHomeStackResizable()
                            && mHomeStack.matchParentBounds())) {
                    final int orientation = mHomeStack.getOrientation();
                    if (orientation != SCREEN_ORIENTATION_UNSET) {
                        return orientation;
                    }
                }
                return SCREEN_ORIENTATION_UNSPECIFIED;
            }

            final int orientation = super.getOrientation();
            boolean isCar = mWmService.mContext.getPackageManager().hasSystemFeature(
                    PackageManager.FEATURE_AUTOMOTIVE);
            if (isCar) {
                // In a car, you cannot physically rotate the screen, so it doesn't make sense to
                // allow anything but the default orientation.
                if (DEBUG_ORIENTATION) Slog.v(TAG_WM,
                        "Forcing UNSPECIFIED orientation in car for display id=" + mDisplayId
                                + ". Ignoring " + orientation);
                return SCREEN_ORIENTATION_UNSPECIFIED;
            }

            if (orientation != SCREEN_ORIENTATION_UNSET
                    && orientation != SCREEN_ORIENTATION_BEHIND) {
                if (DEBUG_ORIENTATION) Slog.v(TAG_WM,
                        "App is requesting an orientation, return " + orientation
                                + " for display id=" + mDisplayId);
                return orientation;
            }

            if (DEBUG_ORIENTATION) Slog.v(TAG_WM,
                    "No app is requesting an orientation, return " + mLastOrientation
                            + " for display id=" + mDisplayId);
            // The next app has not been requested to be visible, so we keep the current orientation
            // to prevent freezing/unfreezing the display too early.
            return mLastOrientation;
        }