只需在你的清单中添加这一行:

android:screenOrientation="portrait"

如:

<manifest
    package="com.example.speedtest"
    android:versionCode="1"
    android:versionName="1.0" >

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

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

    </application>

</manifest>

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);
}

如果你不想经历在每个活动清单条目中添加方向的麻烦，创建一个BaseActivity类(继承' activity '或'AppCompatActivity')，它将被你的应用程序的每个活动继承，而不是' activity '或'AppCompatActivity'，只需在你的BaseActivity中添加以下代码段:

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setRequestedOrientation (ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    // rest of your code......
}

在Kotlin中，同样可以使用下面的代码以编程方式实现:

requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_PORTRAIT

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.

你可以通过在manifest.xml文件中这样写来强制你的特定活动始终保持纵向模式:

<activity
    android:name=".MainActivity"
    android:screenOrientation="portrait"></activity>

你也可以通过在你的活动的onCreate()方法中写入下面的行来强制你的活动保持在纵向模式:

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.your_layout);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
}