`FATAL EXCEPTION: main
Process: dp.develop.ru.startandroid.dp_6, PID: 8603
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(App    CompatViewInflater.java:293)
//много всякого
Caused by: java.lang.reflect.InvocationTargetException
//много всякого
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.CalendarView.setShowWeekNumber(boolean)' on a null object reference`
//много всякого

public class MainActivity extends AppCompatActivity {
TextView DenNedeli;   final int DIALOG = 1; LinearLayout linview;
CalendarView calendarView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    DenNedeli = (TextView) findViewById(R.id.DenNedeli);
    long date = System.currentTimeMillis();
    SimpleDateFormat sdf = new SimpleDateFormat("EEEE");
    String dateString = sdf.format(date);
    DenNedeli.setText(dateString);
}

public void onclick(View view) {
    showDialog(DIALOG);
}

@Override
protected Dialog onCreateDialog(int id) {
    AlertDialog.Builder adb = new AlertDialog.Builder(MainActivity.this);
    adb.setTitle("Выбор даты");
    linview = (LinearLayout) getLayoutInflater()
            .inflate(R.layout.calendarik, null);
    return adb.create();
}

@Override
protected void onPrepareDialog(int id, Dialog dialog) {
    super.onPrepareDialog(id, dialog);
    if (id == DIALOG) {
        calendarView = (CalendarView) dialog.getWindow().findViewById(R.id.calendarView);
        calendarView.setShowWeekNumber(false);
        calendarView.setFirstDayOfWeek(1);
        }
}