显示相关

屏幕朝向

https://developer.android.com/reference/android/content/res/Configuration.html#orientation
具体区别如下：

activity.getResources().getConfiguration().orientation获取的是当前设备的实际屏幕方向值，可以动态地根据设备的旋转或用户的操作进行改变。例如，当用户将设备从纵向旋转到横向时，获取到的屏幕方向值也会相应地改变。

Manifest中配置的orientation是用于指定活动的默认方向，即在没有其他因素影响时，活动应该显示的方向。它可以有以下几个值：

portrait：纵向（竖屏）方向。
landscape：横向（横屏）方向。
sensor：根据设备的旋转自动调整方向。
user：根据用户的偏好自动调整方向。

这个配置可以在Manifest文件中的标签中进行设置。但是，它只是一个默认值，实际的屏幕方向还会受到其他因素的影响，如设备旋转、用户操作等。
activity.getResources().getConfiguration().orientation获取的是当前设备的屏幕方向值，而Manifest中配置的orientation是用于指定活动的默认方向。

总结来说，activity.getResources().getConfiguration().orientation获取的是当前设备的实际屏幕方向值，而Manifest中配置的orientation是活动的默认方向，但实际方向可能会根据设备和用户的操作而改变。

Android屏幕朝向

ORIENTATION_UNDEFINED：未指定
ORIENTATION_PORTRAIT：竖屏
ORIENTATION_LANDSCAPE：横屏
ORIENTATION_SQUARE：正方形

/** Constant for {@link #orientation}: a value indicating that no value has been set. */
public static final int ORIENTATION_UNDEFINED = 0;
/** Constant for {@link #orientation}, value corresponding to the
 * <a href="{@docRoot}guide/topics/resources/providing-resources.html#OrientationQualifier">port</a>
 * resource qualifier. */
public static final int ORIENTATION_PORTRAIT = 1;
/** Constant for {@link #orientation}, value corresponding to the
 * <a href="{@docRoot}guide/topics/resources/providing-resources.html#OrientationQualifier">land</a>
 * resource qualifier. */
public static final int ORIENTATION_LANDSCAPE = 2;
/** @deprecated Not currently supported or used. */
@Deprecated public static final int ORIENTATION_SQUARE = 3;

官方

android:screenOrientation

landscape(常用)	屏幕方向为横向（显示的宽度大于高度）。
portrait(常用)	屏幕方向为纵向（显示的高度大于宽度）。
sensor(常用)	屏幕方向由设备方向传感器决定。显示方向取决于用户如何手持设备，它会在用户旋转设备时发生变化。但在默认情况下，一些设备不会旋转为所有四种可能的方向。如要支持所有这四种方向，请使用 "fullSensor"。即使用户锁定基于传感器的旋转，系统仍可使用传感器。
fullSensor(常用)	屏幕方向由使用 4 种方向中任一方向的设备方向传感器决定。这与 "sensor" 类似，不同之处在于无论设备在正常情况下使用哪种方向，该值均支持所有 4 种可能的屏幕方向（例如，一些设备正常情况下不使用反向纵向或反向横向，但其支持这些方向）。API9 新增
unspecified	默认值。由系统选择方向。在不同设备上，系统使用的政策以及基于政策在特定上下文中所做的选择可能会有所差异。
behind	与 Activity 栈中紧接其后的 Activity 的方向相同。
reverseLandscape	屏幕方向是与正常横向方向相反的横向。API9 新增
reversePortrait	屏幕方向是与正常纵向方向相反的纵向。API9 新增
sensorLandscape	屏幕方向为横向，但可根据设备传感器调整为正常或反向的横向。即使用户锁定基于传感器的旋转，系统仍可使用传感器。API9 新增
sensorPortrait	屏幕方向为纵向，但可根据设备传感器调整为正常或反向的纵向。即使用户锁定基于传感器的旋转，系统仍可使用传感器。API9 新增
userLandscape	屏幕方向为横向，但可根据设备传感器和用户首选项调整为正常或反向的横向。API18 新增
userPortrait	屏幕方向为纵向，但可根据设备传感器和用户首选项调整为正常或反向的纵向。API18 新增
nosensor	确定屏幕方向时不考虑物理方向传感器。系统会忽略传感器，因此显示内容不会随用户手持设备的方向而旋转。
user	用户当前的首选方向。
fullUser	如果用户锁定基于传感器的旋转，则其行为与 user 相同，否则，其行为与 fullSensor 相同，并且支持所有 4 种可能的屏幕方向。API18 新增
locked	将屏幕方向锁定为其当前的任意旋转方向。API18 新增

android:configChanges

方法 onConfigurationChanged

Called by the system when the device configuration changes while your activity is running. Note that this will only be called if you have selected android:configChanges you would like to handle with the R.attr.configChanges attribute in your manifest. If any configuration change occurs that is not selected to be reported by that attribute, then instead of reporting it the system will stop and restart the activity (to have it launched with the new configuration).
At the time that this function has been called, your Resources object will have been updated to return resource values matching the new configuration.

方法 onSaveInstanceState

**Called to retrieve per-instance state from an activity before being killed so that the state can be restored in onCreate(Bundle) or onRestoreInstanceState(Bundle) (the Bundle populated by this method will be passed to both).

This method is called before an activity may be killed so that when it comes back some time in the future it can restore its state. For example, if activity B is launched in front of activity A, and at some point activity A is killed to reclaim resources, activity A will have a chance to save the current state of its user interface via this method so that when the user returns to activity A, the state of the user interface can be restored via onCreate(Bundle) or onRestoreInstanceState(Bundle).

The default implementation takes care of most of the UI per-instance state for you by calling View.onSaveInstanceState() on each view in the hierarchy that has an id, and by saving the id of the currently focused view (all of which is restored by the default implementation of onRestoreInstanceState(Bundle)). If you override this method to save additional information not captured by each individual view, you will likely want to call through to the default implementation, otherwise be prepared to save all of the state of each view yourself.

If called, this method will occur after onStop() for applications targeting platforms starting with Build.VERSION_CODES.P(28). For applications targeting earlier platform versions this method will occur before onStop() and there are no guarantees about whether it will occur before or after onPause().**

方法 onRestoreInstanceState

This method is called after onStart() when the activity is being re-initialized from a previously saved state, given here in savedInstanceState. Most implementations will simply use onCreate(Bundle) to restore their state, but it is sometimes convenient to do it here after all of the initialization has been done or to allow subclasses to decide whether to use your default implementation. The default implementation of this method performs a restore of any view state that had previously been frozen by onSaveInstanceState(Bundle).

This method is called between onStart() and onPostCreate(Bundle). This method is called only when recreating an activity; the method isn’t invoked if onStart() is called for any other reason

Configuration

参考连接

横竖屏切换 屏幕适配 状态保存与恢复