Sort an arraylist of custom object in android

Question

There is an object like this:

dataObj
=============
name
address
isTopPriority

So I have an arrayList of dataObj, how to sort the dataObj to "if isTopPriority is true, then they will be the fronter part of the array" ? Thanks

Attempt the code like:

private class CustomComparator implements Comparator<Spot> {
        @Override
        public int compare(Spot lhs, Spot rhs) {
            // TODO Auto-generated method stub
            return lhs.isStar.compareTo();
        }
    }

But I am confused about why to compare between 2 object , I would like to comapre like this:

just if (currentObj.isFirstPriority == true) then return the object.

Thanks for helping

possible duplicate of Sort ArrayList of custom Objects by property — user180100
– user180100, Commented Apr 1, 2014 at 6:17

ddmps · Accepted Answer · 2014-04-01 06:18:16Z

1

A Comparator "has" to return -1 if rhs is "more" than lhs, 0 if they're equal and 1 if it's less. This is so the sorting is actually consistent (if you sort rhs comparing it to lhs and lhs comparing it to rhs it has to have the opposite result, or 0). The following Comparator does that:

private class CustomComparator implements Comparator<Spot> {
    @Override
    public int compare(Spot lhs, Spot rhs) {
        if (lhs.isStar == rhs.isStar) return 0;
        else if (lhs.isStar) return 1;
        return -1;
    }
}

You also have to actually sort it, but I'm guessing you know how to do that (Collections.sort(arrayList, comparator)).

answered Apr 1, 2014 at 6:18

ddmps

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1 Comment

user782104 Over a year ago

the problem is it seems the sort is reverse, that means the star item is lower prioirty

Autocrab · Accepted Answer · 2014-04-01 06:26:53Z

1

This will sort primary by priority, and secondary by name.

private static final Comparator<Data> dataComparator = new Comparator<Data>() {
    @Override
    public int compare(Data o1, Data o2) {
        if (o1.isTopPriority() && o2.isTopPriority())
            return o1.getName().compareTo(o2.getName());
        if (o1.isTopPriority())
            return 1;
        if (o2.isTopPriority())
            return -1;
        return o1.getName().compareTo(o2.getName());
    }
};

answered Apr 1, 2014 at 6:26

Autocrab

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