How to return a value from void in android

Question

Hello I m new to android development I m developing an app which requires to get the hour and minute from timePicker so I did like this to get it:

public class MainActivity extends Activity {

TimePicker timePicker;
 int hour, changedHour;
 int minute, changedMinute;
TextView tv, tv1;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    tv = (TextView) findViewById(R.id.textView1);
    tv1 = (TextView) findViewById(R.id.textView2);
    timePicker = (TimePicker) findViewById(R.id.timePicker1);
    setCurrentTime();
    timePicker.setOnTimeChangedListener(new OnTimeChangedListener() {

        @Override
        public void onTimeChanged(TimePicker arg0, int hourOfDay,
                int minuteOf) {
            // TODO Auto-generated method stub
            Toast.makeText(getApplicationContext(), "Time set!",
                    Toast.LENGTH_SHORT).show();
            changedHour = hourOfDay;
            changedMinute = minuteOf;

            tv.setText("Hour of Day is " + changedHour + " and Minute is "
                    + changedMinute);
        }

    });
    tv1.setText("Hour of Day is " + changedHour + " and Minute is "
                    + changedMinute);
}

public void setCurrentTime() {
    // TODO Auto-generated method stub
    final Calendar c = Calendar.getInstance();

    hour = c.get(Calendar.HOUR_OF_DAY);
    minute = c.get(Calendar.MINUTE);

    timePicker.setCurrentHour(hour);
    timePicker.setCurrentMinute(minute);

}`

The problem is here

changedHour = hourOfDay;
            changedMinute = minuteOf;

            tv.setText("Hour of Day is " + changedHour + " and Minute is "
                    + changedMinute);

I got the changed time and I set it like hour would be in hourOfDay = changedHour and same for minute now outside the method when I m trying to use the variables the problem is its set to 0 HERE

tv1.setText("Hour of Day is " + changedHour + " and Minute is "
            + changedMinute);

Please help me!

Answer 1

You never actually assign to the changedHour or changedMinute variables before you print them using tv1.setText, since it's very likely that onTimeChanged hasn't ever fired by that point. For this reason, they'll have their default values of 0, since they haven't been assigned anything else yet.

Anyway, you can't return values out of a void function. By definition, void is a lack of a type.

How to fix this depends on how exactly you want the code to work. The path of least resistance would be to set changedHour and changedMinute from within setCurrentTime, e.g.

public void setCurrentTime() {
    // TODO Auto-generated method stub
    final Calendar c = Calendar.getInstance();

    hour = c.get(Calendar.HOUR_OF_DAY);
    minute = c.get(Calendar.MINUTE);

    // NEW CODE
    changedHour = hour;
    changedMinute = minute;
    // END NEW CODE

    timePicker.setCurrentHour(hour);
    timePicker.setCurrentMinute(minute);

}

You could return the hour and minute through some other mechanism (return a struct or use out parameters), but given that you update changedHour/Minute in your onTImeChanged callback, it probably wouldn't fit well with the existing flow.

On a re-read though, this could all just be because you're using the wrong variable in tv1.setText. You assign to the class variables hour and minute in setCurrentTime, so you could just print those rather than changedHour and changedMinute, e.g.

tv1.setText("Hour of Day is " + hour + " and Minute is "
                + minute);