When I run program then my emulator stops
1st main class name is MainActivity.java
public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button b= (Button) findViewById(R.id.button1);
        b.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(MainActivity.this, AndroidExplorer.class));
            }
        });
    }
2nd class name is AndroidExplorer.java
public class AndroidExplorer extends ListActivity 
{
    private List<String> item = null;
    private List<String> path = null;
    private String root="/";
    private TextView myPath;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        myPath = (TextView)findViewById(R.id.path);
        getDir(root);
    }
    private void getDir(String dirPath)
    {
        myPath.setText("Location: " + dirPath);
        item = new ArrayList<String>();
        path = new ArrayList<String>();
        File f = new File(dirPath);
        File[] files = f.listFiles();
        if(!dirPath.equals(root))
        {
            item.add(root);
            path.add(root);
            item.add("../");
            path.add(f.getParent());
        }
        for(int i=0; i < files.length; i++)
        {
                File file = files[i];
                path.add(file.getPath());
                if(file.isDirectory())
                    item.add(file.getName() + "/");
                else
                    item.add(file.getName());
        }
        ArrayAdapter<String> fileList =
            new ArrayAdapter<String>(this, R.layout.row, item);
        setListAdapter(fileList);
    }
    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        File file = new File(path.get(position));
        if (file.isDirectory())
        {
            if(file.canRead())
                getDir(path.get(position));
            else
            {
                new AlertDialog.Builder(this)
                .setIcon(R.drawable.icon)
                .setTitle("[" + file.getName() + "] folder can't be read!")
                .setPositiveButton("OK", 
                        new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                // TODO Auto-generated method stub
                            }
                        }).show();
            }
        }
        else
        {
            new AlertDialog.Builder(this)
                .setIcon(R.drawable.icon)
                .setTitle("[" + file.getName() + "]")
                .setPositiveButton("OK", 
                        new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                // TODO Auto-generated method stub
                            }
                        }).show();
        }
    }}
Logcat Output:
 06-12 00:40:17.718: E/AndroidRuntime(12701): FATAL EXCEPTION: main
 06-12 00:40:17.718: E/AndroidRuntime(12701): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.fyp.ftpfilesharing/com.fyp.ftpfilesharing.MainActivity}: java.lang.ClassCastException: android.widget.RelativeLayout 
 
     
    