<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="in.co.nurture.bajajfinserv">
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>

    <application

        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity" android:screenOrientation="portrait">

            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

我们可以使用属性或android:screenOrientation来限制活动在纵向或横向模式。

如果我们在程序中有多个活动，那么我们可以自由地限制任何模式下的任何一个活动，它不会影响你不想要的其他活动。

如果您正在使用Xamarin c#，其中一些解决方案将无法工作。这是我发现的一个有效的解决方案。

[Activity(MainLauncher = true, Icon = "@drawable/icon", ScreenOrientation = ScreenOrientation.Portrait)]

上面的类工作得很好，类似于其他解决方案。此外，它不是全局适用的，需要放在每个活动头中。

将android:screenOrientation="portrait"添加到AndroidManifest.xml中的活动中。例如:

<activity android:name=".SomeActivity"
          android:label="@string/app_name"
          android:screenOrientation="portrait" />

由于这已经成为一个超级流行的答案，我感到非常内疚，因为强制肖像很少是它经常应用的问题的正确解决方案。 强制肖像的主要注意事项:

This does not absolve you of having to think about activity lifecycle events or properly saving/restoring state. There are plenty of things besides app rotation that can trigger an activity destruction/recreation, including unavoidable things like multitasking. There are no shortcuts; learn to use bundles and retainInstance fragments. Keep in mind that unlike the fairly uniform iPhone experience, there are some devices where portrait is not the clearly popular orientation. When users are on devices with hardware keyboards or game pads a la the Nvidia Shield, on Chromebooks, on foldables, or on Samsung DeX, forcing portrait can make your app experience either limiting or a giant usability hassle. If your app doesn't have a strong UX argument that would lead to a negative experience for supporting other orientations, you should probably not force landscape. I'm talking about things like "this is a cash register app for one specific model of tablet always used in a fixed hardware dock."

所以大多数应用程序应该让手机传感器、软件和物理配置自己决定用户想要如何与你的应用程序交互。但是，如果你对你的用例中传感器方向的默认行为不满意，你可能仍然需要考虑一些情况:

If your main concern is accidental orientation changes mid-activity that you think the device's sensors and software won't cope with well (for example, in a tilt-based game) consider supporting landscape and portrait, but using nosensor for the orientation. This forces landscape on most tablets and portrait on most phones, but I still wouldn't recommend this for most "normal" apps (some users just like to type in the landscape softkeyboard on their phones, and many tablet users read in portrait - and you should let them). If you still need to force portrait for some reason, sensorPortrait may be better than portrait for Android 2.3 (Gingerbread) and later; this allows for upside-down portrait, which is quite common in tablet usage.

如果你的活动与第一个设备朝向状态相关，在onCreate方法中获取当前设备朝向，然后永远修复它:

int deviceRotation = ((WindowManager) getBaseContext().getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay().getOrientation();

if(deviceRotation == Surface.ROTATION_0) {
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
}
else if(deviceRotation == Surface.ROTATION_180)
{
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_REVERSE_PORTRAIT);
}
else if(deviceRotation == Surface.ROTATION_90)
{
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
}
else if(deviceRotation == Surface.ROTATION_270)
{
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE);
}

在阅读这篇文章之前，我不知道AndroidManifest.xml文件开关，所以在我的应用程序中，我使用了这个代替:

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); // Fixed portrait orientation

如果你想禁用Android应用程序(或单个活动)的横向模式，你需要做的就是添加:

android:screenOrientation="portrait"到AndroidManifest.xml文件中的活动标签。

如:

<activity 
    android:name="YourActivityName"
    android:icon="@drawable/ic_launcher"
    android:label="Your App Name"
    android:screenOrientation="portrait">

另一种方法:程序化方法。

如果您希望以编程方式完成此操作，即使用Java代码。您可以在不希望以横向模式显示的活动的Java类中添加以下代码。

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);