Hesam Hesam - 17 days ago 13
Android Question

How to get text direction in Android and change layout dynamically according to the direction?

I'm doing some research about feasibility of changing UI dynamically based on direction of a text. Although Google is supporting RTL languages (ref: Native RTL support in Android 4.2) but it doesn't cover a situation that application has mix of LTR and RTL contents.

Google's solution is right if we have multilingual app and it has different sources of static data (such as menu items) in different languages. However, I didn't find any other document regard how to change layout dynamically based on direction of text content.

Following image shows current design of my test app. List comes from Facebook (list of my friends) and contains English and Persian names.

enter image description here

My solution is having two layouts (one for LTR and one for RTL) in adapter and assigning each one based on direction of name. So, I wrote following lines of code:

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
ViewHolder holder;

if(position % 2 == 0)
convertView = myInflater.inflate(R.layout.list_add_friends_row, null);
else
convertView = myInflater.inflate(R.layout.list_add_friends_row_mirror, null);

holder = new ViewHolder();

holder.llSection = (LinearLayout) convertView.findViewById(R.id.section);
holder.tvUserName = (TextView) convertView.findViewById(R.id.tvUserName);
holder.ivPicture = (ImageView) convertView.findViewById(R.id.ivPicture);
holder.btnAdd = (Button) convertView.findViewById(R.id.btnAdd);

convertView.setTag(holder);



holder.btnAdd.setTag(position);
holder.tvUserName.setText(userList.get(position).getName());
imageDownloader.displayImage(holder.ivPicture, userList.get(position).getPhotoUrl());

...

return convertView;
}


and result is:

enter image description here

I mirrored rows based on if row is even or odd.
Now, my question is how to mirror UI based on name. I think I should change clause condition from
if(position % 2 == 0)
to something like
if(isNameLTR(FIRST_CHAR_OF_NAME))
. I have no idea how to implement this method.

How can I know a character is LTR ot RTL?
(I think Android knows first character of word is RTL or LTR that's why when width of text view is match parent it align text to right if character is RLT and to left if character is LTR).

Any suggestion or comments would be appreciated. Thanks

Answer

Solution, was easier that I was thinking :) Thanks to JAVA

There is Bidi class. This class has getBaseLevel() method which returns 0 if your text is left-to-right otherwise 1 (if right-to-left).

So, this is my code:

@Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        ViewHolder holder;

        Bidi bidi = new Bidi(userList.get(position).getName(), Bidi.DIRECTION_DEFAULT_LEFT_TO_RIGHT);
        if(bidi.getBaseLevel() == 0)
            convertView = myInflater.inflate(R.layout.list_add_friends_row, null);
        else
            convertView = myInflater.inflate(R.layout.list_add_friends_row_mirror, null);

...

and result is:

enter image description here

=============

Update:

There is another method, baseIsLeftToRight() that might be better to be used in if statement. Result was same as above.

Bidi bidi = new Bidi(userList.get(position).getName(), Bidi.DIRECTION_DEFAULT_LEFT_TO_RIGHT);
if(bidi.baseIsLeftToRight())
                convertView = myInflater.inflate(R.layout.list_add_friends_row, null);
            else
                convertView = myInflater.inflate(R.layout.list_add_friends_row_mirror, null);
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