Question

I have a spinner which is populated from an Enum:

public enum Frequencies
    {
    EVERYDAY("Every day"), EVERYOTHERDAY("Every second day");

    private String friendlyName;

    private Frequencies(String friendlyName)
    {
        this.friendlyName = friendlyName;
    }

    @Override public String toString()
    {
        return friendlyName;
    }
    };

The toString() overrides means the spinner displays user friendly names.

The spinner is populated like so:

        ArrayAdapter<Frequencies> adapter = new ArrayAdapter<Frequencies>(this, android.R.layout.simple_spinner_item, 
            Frequencies.values());
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    newAlarmFreqSpinner.setAdapter(adapter);

All of this is working well. When the user chooses a frequency from the spinner, I’d like to use the value to set a long value to represent the interval between alarms in a simple Alarm object. So the value for “Every day” would be the number of seconds in one day.

However, I can’t quite get my head around how to elegantly handle the Frequency object I retrieve from the spinner. My initial thought was to use a switch statement to switch on the displayed string to determine the long value I require, but of course you can’t switch on a string.

I then tried modifying the Frequencies enum so each entry stored its own long value:

    EVERYDAY("Every day", 86400), EVERYOTHERDAY("Every second day", 86400 * 2);

private String friendlyName;
public final int intervalInSecs;

private Frequencies(String friendlyName, int intervalInSecs)
{
    this.friendlyName = friendlyName;
    this.intervalInSecs = intervalInSecs;
}...

But the switch then complains that “case expressions must be constant expressions” (even though I’ve made intervalInSecs final):

    Object obj = newAlarmFreqSpinner.getSelectedItem();
    switch(((Frequencies)obj).getIntervalInSecs())
{
    case Frequencies.EVERYDAY.intervalInSecs: //Java doesn't like this
    {

        break;
    }...

I’m sure I’m making this more difficult than it really is! I’d appreciate any ideas.

Answer 1

Well basically the enum type has it’s associated interval. So you don’t need to switch on the interval, just switch on the enum type:

Object obj = newAlarmFreqSpinner.getSelectedItem();
switch((Frequencies)obj) {
case Frequencies.EVERYDAY {
    alarm.setInterval(EVERYDAY.getIntervalInSecs());
    break;
}...