Android：按钮OnClick在SherlockFragment中不起作用

Question

I've tab activity in which i want to use a button, but when i click on button, it force closes the app. Can you please tell me what is going on, i am new to Android.

 public class HomeActivity extends SherlockFragment {
    private Button bt;
    private Context con;


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.home_layout, container, false);
        bt = (Button)rootView.findViewById(R.id.btn);
        bt.setOnClickListener(new View.OnClickListener(){
            @Override public void onClick(View v)
            {

                Toast.makeText(con, "hello", Toast.LENGTH_LONG).show();

            }       
        });

        return rootView;

    }


}

Answer 1

when i click on button, it force closes the app

Because con object of Context is null . which is used for showing Toast message in Button onClick method.

Do it as:

 Toast.makeText(v.getContext(), "hello", Toast.LENGTH_LONG).show();

And initialize con object by calling getActivity() in onCreateView as:

con=getActivity();

Answer 2

If you can avoid that, don't keep a reference to the context; instead of the

private Context con;

get the current Activity in the code, so use

Toast.makeText(getActivity(), "hello", Toast.LENGTH_LONG).show();

Btw, this seems to be the cause of your crash, as Context is null.