Source not found Exception while setting layoutparameters

Hi I'm new to android world. I'm working on an application that supports arabic and english languages.So I made my design for english language in the xml and through the code when the user wants to work with arabic language I change the gravity of my widgets to match the arabic right-to-left look.

Now I have 2 questions:- 1-Will I have to implement virtual arabic keyboard?

2-I have a list that shows a forum's threads to start from right-to-left.To make this list I have 2 xmls one for the list and the other for the list's row. When the user's language is arabic I make ALIGN_PARENT_RIGHT for each widget in my xmls. It works for the list xml but 开发者_如何学Cwhen I try to make this for the list's row It throws source not found exception.

Could help me?

    //threads row
//lastPost
tvThread=(TextView)findViewById(R.id.txtLastPost);

    //here it throws the exception
params = (RelativeLayout.LayoutParams)tvThread.getLayoutParams();
params.setMargins(20, 0, 0, 0);

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If your TextView is contained within some other Layout Element, and not a direct child of your RelativeLayout (likely) you shouldn't cast it's params as relativelayout. Cast it as whatever it's container layout is, or just use generic LayoutParams. Should work fine as

// params defined somewhere previously as something like LayoutParams params;
params = tvThread.getLayoutParams();
params.setMargins(20, 0, 0, 0);