Question

in programming for android, my use of setOnItemClickListener is now throwing an exception. I’ve never had any trouble with it before and I didn’t see any exceptions listed for it in the documentation. Can anybody tell me what the problem is?

package com.name.magicwindow;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class MagicWindowActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ListView mainMenu;
        try{
            mainMenu = (ListView)findViewById(R.id.main_menu_list);

            try{
                mainMenu.setOnItemClickListener(new OnItemClickListener()
                {
                    public void onItemClick(AdapterView<?> parent,View view,int position,long id)
                    {
                        // When clicked, show a toast with the TextView text
                        Toast.makeText(getApplicationContext(), ((TextView) view).getText(),Toast.LENGTH_SHORT).show();
                    }
                });
            }catch(Exception e)
            {
                Toast.makeText(getApplicationContext(), "could not set listener",Toast.LENGTH_LONG).show();
            }
        }catch(Exception e)
        {
            Toast.makeText(getApplicationContext(), "could not find listview",Toast.LENGTH_LONG).show();
        }


        setContentView(R.layout.main);
    }
}

Answer 1

That one should be pretty simple:

You have to call setContentView(R.layout.main) before you use findViewById().
So your activity knows what it’s content (view hierarchy) is.