求帮忙看看

public class MainActivity extends AppCompatActivity implements TimePicker.OnTimeChangedListener{
private TimePicker timePicker;
private Calendar cal;
private int year;//定义时间变量
private int month;
private int day;
private int hour;
private int minute;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
timePicker = (TimePicker) findViewById(R.id.timePicker);
cal = Calendar.getInstance();//获取时间信息
//获取年月日的信息
hour=cal.get(Calendar.HOUR);
minute=cal.get(Calendar.MINUTE);
setTitle(hour+":"+minute);
timePicker.setOnTimeChangedListener(this);
}
@Override
public void onTimeChanged(TimePicker view, int hourOfDay, int minute) {
setTitle(hour +":"+ minute);
}为什么标题栏的时间和设置的时间的小时不同步