Launcher默认支持旋转

<SwitchPreference
        android:key="pref_allowRotation"
        android:title="@string/allow_rotation_title"
        android:summary="@string/allow_rotation_desc"
        android:defaultValue="@bool/allow_rotation"
        android:persistent="true" />

    public static boolean getAllowRotationDefaultValue(DeviceProfile deviceProfile) {
        // If the device's pixel density was scaled (usually via settings for A11y), use the
        // original dimensions to determine if rotation is allowed of not.
        float originalSmallestWidth = dpiFromPx(
                Math.min(deviceProfile.widthPx, deviceProfile.heightPx), DENSITY_DEVICE_STABLE);
        return true;
    }

public static final String ALLOW_ROTATION_PREFERENCE_KEY = "pref_allowRotation";
...
public static boolean getAllowRotationDefaultValue(Context context) {
    //默认支持旋转，这里直接return true
        if (context != null && context.getResources().getBoolean(R.bool.allow_rotation)){
            return true;
        }
        // If the device's pixel density was scaled (usually via settings for A11y), use the
        // original dimensions to determine if rotation is allowed of not.
        Resources res = Resources.getSystem();
        int originalSmallestWidth = res.getConfiguration().smallestScreenWidthDp
                * res.getDisplayMetrics().densityDpi / DENSITY_DEVICE_STABLE;
        return originalSmallestWidth >= 600;
    }

  private void initFlags() {
        SysUINavigationMode.Mode currentMode = SysUINavigationMode.getMode(mContext);
        boolean rotationWatcherSupported = mOrientationListener.canDetectOrientation() &&
                currentMode != TWO_BUTTONS;
        setFlag(FLAG_ROTATION_WATCHER_SUPPORTED, rotationWatcherSupported);
 
        // initialize external flags
        updateAutoRotateSetting();
        updateHomeRotationSetting();
    }
    ...
private void updateHomeRotationSetting() {
        setFlag(FLAG_HOME_ROTATION_ALLOWED_IN_PREFS,
                mSharedPrefs.getBoolean(ALLOW_ROTATION_PREFERENCE_KEY, getAllowRotationDefaultValue(mContext)));//这里默认是false
    }