How do I disable orientation change on Android?

Update April 2013: Don't do this. It wasn't a good idea in 2009 when I first answered the question and it really isn't a good idea now. See this answer by hackbod for reasons:

Avoid reloading activity with asynctask on orientation change in android

Add android:configChanges="keyboardHidden|orientation" to your AndroidManifest.xml. This tells the system what configuration changes you are going to handle yourself - in this case by doing nothing.

<activity android:name="MainActivity"
     android:screenOrientation="portrait"
     android:configChanges="keyboardHidden|orientation">

See Developer reference configChanges for more details.

However, your application can be interrupted at any time, e.g. by a phone call, so you really should add code to save the state of your application when it is paused.

Update: As of Android 3.2, you also need to add "screenSize":

<activity
    android:name="MainActivity"
    android:screenOrientation="portrait"
    android:configChanges="keyboardHidden|orientation|screenSize">

From Developer guide Handling the Configuration Change Yourself

Caution: Beginning with Android 3.2 (API level 13), the "screen size" also changes when the device switches between portrait and landscape orientation. Thus, if you want to prevent runtime restarts due to orientation change when developing for API level 13 or higher (as declared by the minSdkVersion and targetSdkVersion attributes), you must include the "screenSize" value in addition to the "orientation" value. That is, you must declare android:configChanges="orientation|screenSize". However, if your application targets API level 12 or lower, then your activity always handles this configuration change itself (this configuration change does not restart your activity, even when running on an Android 3.2 or higher device).

---

You need to modify AndroidManifest.xml as Intrications (previously Ashton) mentioned and make sure the activity handles the onConfigurationChanged event as you want it handled. This is how it should look:

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
}

---

I've always found you need both

android:screenOrientation="nosensor" android:configChanges="keyboardHidden|orientation"

---

As said, set android:configChanges of your Activity (in manifest file) to keyboardHidden|orientation and then:

1) Override onConfigurationChanged()

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    //here you can handle orientation change
}

2) Add this line to your activity's onCreate()

setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

It's better than add same line to onConfigurationChanged, because your app will turn to portrait mode and then back to landscape (it will happen only one time, but it's annoying).

Also you can set android:screenOrientation="nosensor" for your activity (in manifest). But using this way you're a not able to handle orientation changes at all.

---

Use this..

    android:screenOrientation="portrait"

---

In OnCreate method of your activity use this code:

    @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

Now your orientation will be set to portrait and will never change.

---

In the AndroidManifest.xml file, for each activity you want to lock add the last screenOrientation line:

android:label="@string/app_name"
android:name=".Login"
android:screenOrientation="portrait" >

Or android:screenOrientation="landscape".

---

In your androidmanifest.xml file:

   <activity android:name="MainActivity" android:configChanges="keyboardHidden|orientation">

or

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
}

---

To lock the screen by code you have to use the actual rotation of the screen (0, 90, 180, 270) and you have to know the natural position of it, in a smartphone the natural position will be portrait and in a tablet, it will be landscape.

Here's the code (lock and unlock methods), it has been tested in some devices (smartphones and tablets) and it works great.

public static void lockScreenOrientation(Activity activity)
{   
    WindowManager windowManager =  (WindowManager) activity.getSystemService(Context.WINDOW_SERVICE);   
    Configuration configuration = activity.getResources().getConfiguration();   
    int rotation = windowManager.getDefaultDisplay().getRotation(); 

    // Search for the natural position of the device    
    if(configuration.orientation == Configuration.ORIENTATION_LANDSCAPE &&  
       (rotation == Surface.ROTATION_0 || rotation == Surface.ROTATION_180) ||  
       configuration.orientation == Configuration.ORIENTATION_PORTRAIT &&   
       (rotation == Surface.ROTATION_90 || rotation == Surface.ROTATION_270))   
    {   
        // Natural position is Landscape    
        switch (rotation)   
        {   
            case Surface.ROTATION_0:    
                activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);    
                break;      
            case Surface.ROTATION_90:   
                activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_REVERSE_PORTRAIT); 
            break;      
            case Surface.ROTATION_180: 
                activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE); 
                break;          
            case Surface.ROTATION_270: 
                activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); 
                break;
        }
    }
    else
    {
        // Natural position is Portrait
        switch (rotation) 
        {
            case Surface.ROTATION_0: 
                activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); 
            break;   
            case Surface.ROTATION_90: 
                activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE); 
            break;   
            case Surface.ROTATION_180: 
                activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_REVERSE_PORTRAIT); 
                break;          
            case Surface.ROTATION_270: 
                activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE); 
                break;
        }
    }
}

public static void unlockScreenOrientation(Activity activity)
{
    activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED);
}

---

Add

android:configChanges="keyboardHidden|orientation|screenSize" 

to your manifest.

---

In Visual Studio Xamarin:

Add:

using Android.Content.PM; to you activity namespace list.

Add:

[Activity(ScreenOrientation = Android.Content.PM.ScreenOrientation.Portrait)]

as an attribute to you class, like that:

[Activity(ScreenOrientation = ScreenOrientation.Portrait)]
public class MainActivity : Activity
{...}

---

You can simply use like below in the application class if you want only PORTRAIT mode for all activities in your app.

class YourApplicationName : Application() {

override fun onCreate() {
    super.onCreate()

    registerActivityLifecycleCallbacks(object : ActivityLifecycleCallbacks {

        override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {
            activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_PORTRAIT
        }

        override fun onActivityStarted(activity: Activity) {

        }

        override fun onActivityResumed(activity: Activity) {

        }

        override fun onActivityPaused(activity: Activity) {

        }

        override fun onActivityStopped(activity: Activity) {

        }

        override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {

        }

        override fun onActivityDestroyed(activity: Activity) {

        }

    })

}

}

---

Please note, none of the methods seems to work now!

In Android Studio 1 one simple way is to add android:screenOrientation="nosensor".

This effectively locks the screen orientation.

---