Add Function When Focus and Remove It When Not Focus

I have a problem with TextWatcher, here is my code

JumlahTrx.setOnFocusChangeListener(new View.OnFocusChangeListener(){
       public void onFocusChange(View v, boolean hasFocus){
           if(v.getId() == R.id.editJumlah && hasFocus){
               JumlahTrx.addTextChangedListener(onTextChangedListener());
           }else{
               if(JumlahTrx!=null) {
                   try{
                       JumlahTrx.removeTextChangedListener(onTextChangedListener());
                   }catch (Throwable e){
                       e.printStackTrace();
                   }
               }
           }
       }
    });

The code doesn't have any error. But the function not work like what i want. I want if JumlahTrx (R.id.editjumlah) is focused then add TextWatcher function, if i click on another EditText or not focus on that remove it.

Any help on my code?