Android how to keep view orientation constant when the device is rotated

Question

There are several stack overflow questions that deal with keeping the activity in a constant orientation, suggesting either to set android:screenOrientation (or this) or to deal with the configuration changes manually.

However, these answers do not solve the problem if one wants to keep the benefits of automatic layout for most of the views, but to keep one view in a constant orientation. For example I have one main view for the content (a bitmap) and optionally several "toolbars". When the device is rotated from portrait to landscape, I want the toolbars to re-layout automatically. On the other hand, the main content view has a bitmap, and this should rotate with the device. Here is a simple code I use in my onDraw:

    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        Bitmap bm = ... // code to get a bitmap
        if (bm != null) {
            canvas.drawBitmap(bm,0,0,mPaint);
        }
    }

This obviously does not work as intended because when the device orientation changes, the view is relayout and its coordinate system rotates in this orientation change by 90 degrees with respect to the physical device. One way to compensate for that would be to use a Matrix-object to draw the bitmap with 90 degrees rotation if the device orientation has changed. However, then also the input coordinates would have to be changed in order to keep the view input points and the point on the bitmap in correspondence.

Therefore my question after this long explanation is: can I keep the view so that its coordinate system with respect to the device is not rotated when the orientation changes.

Here is a picture that expresses what I want and what I currently get (xy coordinate system for the view also illustrated).

Answer 1

Inside your activity in manifest xml use the screen orientation attribut with portrait value

Like

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

Answer 2

I am not sure but you should try following

1. put one xml in layout folder which indicate portrait layout
2. create one folder named it layout-land
3. put xml which indicate landscape layout with same name as in layout folder

Android automatically take that layout from land-layout when you will rotate your screen to landscape.

Another way

Activity will be restarted when orientation is changed so make to layout for that activity and you can set layout to your activity as per orientation.

if (getResources().getConfiguration().orientation==Configuration.ORIENTATION_LANDSCAPE)
{
   setContentView(R.layout.landscape_layout);
}
else
{
   setContentView(R.layout.portrait_layout);
}

Hope it will help you.

Answer 3

You can check the orientation and redraw your View after orientation will be changed

if (getResources().getConfiguration().orientation==Configuration.ORIENTATION_LANDSCAPE)
{
//...
}
else
{
//...
}

Answer 4

Use this code in your Manifest

<uses-permission android:name="android.permission.SET_ORIENTATION"/>
<activity
        android:name="com.package.MyActivity"
        android:configChanges="keyboardHidden|orientation"
        android:screenOrientation="portrait" >
    </activity>

Answer 5

Well, first of all, you will not need two layouts. Create only one xml with an image view and a layout which has property align parent bottom set to true.

Now as per the images you have provided, you want to rotate the image anticlockwise when your device is in landscape. For that , you can use my image rotation code :-

You can always check the rotation of the image using Matrix and rotate it accordingly.

This code goes in onCreate--> The code below is to rotate the image when taken from camera or gallery. You can modify according to your needs. I have put comments below to simplify understanding.

        BitmapFactory.Options bmOptions = new BitmapFactory.Options();
        bmOptions.inJustDecodeBounds = false;
        bmOptions.inPurgeable = true;

            Bitmap cameraBitmap = BitmapFactory.decodeFile(filePath);//You convert your image view image here in a bitmap
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            cameraBitmap.compress(Bitmap.CompressFormat.JPEG, 100, bos);


            ExifInterface exif = new ExifInterface(filePath);
            float rotation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);  
            System.out.println(rotation);

            float rotationInDegrees = exifToDegrees(rotation);


            System.out.println(rotationInDegrees);
            //These three lines below set the rotation. 
            //Put an if condition here to check device rotation and set the rotation of image view as per the device rotation.
//The line below will help you get device rotation.    
//getResources().getConfiguration().orientation==Configuration.ORIENTATION_LANDSCAPE
                Matrix matrix = new Matrix();
                matrix.postRotate(rotationInDegrees);//Here you set the rotation value in which you want your image view to be rotated
            //If ends here

            Bitmap scaledBitmap = Bitmap.createBitmap(cameraBitmap);
            Bitmap rotatedBitmap = Bitmap.createBitmap(cameraBitmap , 0, 0, scaledBitmap .getWidth(), scaledBitmap .getHeight(), matrix, true);
            FileOutputStream fos=new FileOutputStream(filePath);
            rotatedBitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
            fos.flush();
            fos.close();
                        //this rotatedbitmap you can set in your image view

//onCreate Code Ends here.

//This function below is used to get rotation:-

        private static float exifToDegrees(float exifOrientation) {        
        if (exifOrientation == ExifInterface.ORIENTATION_ROTATE_90) { return 90; } 
        else if (exifOrientation == ExifInterface.ORIENTATION_ROTATE_180) {  return 180; } 
        else if (exifOrientation == ExifInterface.ORIENTATION_ROTATE_270) {  return 270; }            
        return 0;    
     }