SCREEN_ORIENTATION_LANDSCAPE upside down - Why?

问题:

I am using the following code to set orientation locking per user preference:

 private void doLock(boolean locked) {
     if (locked) {
       int o = getResources().getConfiguration().orientation;
       if (o == Configuration.ORIENTATION_LANDSCAPE)
         setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);       
       else if (o == Configuration.ORIENTATION_PORTRAIT)
         setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);       
     } 
     else {
       setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR);
     }
 }

It works, except for the case in which I am in unlocked mode (SCREEN_ORIENTATION_SENSOR) with the screen showing LANDSCAPE correctly (!), then invoke doLock(true) and...

instead of the screen locking to LANDSCAPE in its current (correct) landscape view, it locks to an upside down landscape view. i.e. same exact but flip vertically (y becomes -y).

Why is that and how do I approach this problem in order to fix it?

My initial inquiry reveals that there are quite a few possibilities other than the common two (portrait, landscape), including reverseLandscape, but my hunch tells me that this problem may be device-dependent and so by using it I might be fixing the problem only for my phone but not for all other devices.

Is there a way to force correct landscape orientation (when switched from sensor) in all devices?

To make this clearer and easier to reproduce, here are the steps that exhibit the problem:

1. Start with phone rotated to the right (clockwise), in unlocked mode (SCREEN_ORIENTATION_SENSOR) with the screen showing LANDSCAPE correctly (!),
2. Then invoke doLock(true)
3. Instead of the screen locking to LANDSCAPE in its current (correct) landscape view, it locks to an upside down landscape view. i.e. same exact but flip vertically (y becomes -y).

回答1:

What you are describing is not a bug but rather the expected behavior from Android 2.2 or lower.

@forgivegod provided a theoretically correct approach, except that for Android 2.2 or lower the screenOrientation.reverseLandscape and screenOrientation.reversePortrait values are not recognized, even if faked (as @forgivegod's code does).

I bet you are seeing this problem when you rotate the phone clockwise (rotation=3) but not counter-clockwise (rotation=1).

Try with Android 2.3 or higher and see what happens.

回答2:

Try the following to disable and enable orientation via code (this will work in API level 7 and up) :

public static void disableRotation(Activity activity) {
    final int orientation = activity.getResources().getConfiguration().orientation;
    final int rotation = activity.getWindowManager().getDefaultDisplay()
            .getOrientation();

    // Copied from Android docs, since we don't have these values in Froyo
    // 2.2
    int SCREEN_ORIENTATION_REVERSE_LANDSCAPE = 8;
    int SCREEN_ORIENTATION_REVERSE_PORTRAIT = 9;

    if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.FROYO) {
        SCREEN_ORIENTATION_REVERSE_LANDSCAPE = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE;
        SCREEN_ORIENTATION_REVERSE_PORTRAIT = ActivityInfo.SCREEN_ORIENTATION_PORTRAIT;
    }

    if (rotation == Surface.ROTATION_0 || rotation == Surface.ROTATION_90) {
        if (orientation == Configuration.ORIENTATION_PORTRAIT) {
            activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        } else if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
            activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
        }
    } else if (rotation == Surface.ROTATION_180
            || rotation == Surface.ROTATION_270) {
        if (orientation == Configuration.ORIENTATION_PORTRAIT) {
            activity.setRequestedOrientation(SCREEN_ORIENTATION_REVERSE_PORTRAIT);
        } else if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
            activity.setRequestedOrientation(SCREEN_ORIENTATION_REVERSE_LANDSCAPE);
        }
    }
}

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

回答3:

Simple and functional>

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

    <activity
        android:screenOrientation="sensorLandscape"
    </activity>

  </application>

回答4:

try with universal landscape orientation

private static final int ORIENTATION_90 = 1;
private static final int ORIENTATION_0 = 0;
private static final int ORIENTATION_180 = 2;
private static final int ORIENTATION_270 = 3;

switch (orientation)
    {
      default:
      case ORIENTATION_0: // Portrait
        //dostuff
        break;
      case ORIENTATION_90: // Landscape left
        //do stuff
        break;
      case ORIENTATION_180: // Upside down.
        //do stuff
        break;
      case ORIENTATION_270: // Landscape right
        //do stuff
        break;
      }