Difficulty in iterating over an ArrayList of HashMaps

Question

I have a globally defined ArrayList as ArrayList<Map<String, String>> mContactList;.

Now, in one of the methods, I am defining a HashMap like this:

Map<String, String> NamePhoneType = new HashMap<String, String>();    
NamePhoneType.put("Name", contactName); //contactName is returned from a query
NamePhoneType.put("Phone", phoneNumber); //phoneNumber is returned from a query
mContactList.add(NamePhoneType);

So mContactList now looks like [{Name=Abc, Phone=123}, {Name=def, Phone=456}...]

Now when I try to iterate over the mContactList using the following, I always get the key as 'Phone' and Value as '123' or '456' depending on the index.

public void onItemClick(AdapterView<?> av, View v, int index,long arg) {
    Map<String, String> map = (Map<String, String>) av.getItemAtPosition(index);
    Iterator<String> myVeryOwnIterator = map.keySet().iterator();
    while (myVeryOwnIterator.hasNext()) {
        String key = (String) myVeryOwnIterator.next();
        String value = (String) map.get(key);
        getNumber.setText(value);                                    
        }               
    }
});

I want the Name and the Phone of the selected index in 2 separate strings. How do I do that?

It really seems like you should create a class called "ContactInfo" that has Name and Phone members. Why use arbitrary key/value stores when you can make your model concrete? — dlev
– dlev, Commented Jul 10, 2012 at 21:25

cklab · Accepted Answer · 2012-07-10 21:48:27Z

1

Instead of having a Map as you do, I would recommend creating a class called Contact. Your ArrayList would then be declared as

ArrayList<Contact> mContactList;

The Contact class would look like

public class Contact {
    private String name;
    private String phoneNumber;

    public Contact (String name, String phoneNumber) {
        this.name = name;
        this.phoneNumber = phoneNumber;
    }

    public String getName() {
        return name;
    }

    public String getPhoneNumber() {
        return phoneNumber;
    }
}

Whenever you end up with nested data structures, it's usually a sign to rethink your design as there's usually a better way to do it.

However, to answer your question; note what this piece of code is doing.

Map<String, String> map = (Map<String, String>) av.getItemAtPosition(index);
Iterator<String> myVeryOwnIterator = map.keySet().iterator();
while (myVeryOwnIterator.hasNext()) {
    String key = (String) myVeryOwnIterator.next();
    String value = (String) map.get(key);
    getNumber.setText(value);                                    
}

You are iterating through a map which (appears to) always have two pairs:

"Name", nameValue
"Phone", phoneValue

There's no need to iterate through the Map to get the values you desire. Your code should look like:

Map<String, String> map = (Map<String, String>) av.getItemAtPosition(index);
String phoneNumber = map.get("Phone");
String name = map.get("Name");

edited Jul 10, 2012 at 21:48

answered Jul 10, 2012 at 21:26

cklab

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3 Comments

gsb Over a year ago

thank you so much. Your answer to my question worked. as far as the suggestion goes, when I create a class as you said, how do I set values to the name and phone variables after i retrieve them from the query?

Will Over a year ago

@Nerd add a constructor (or setter methods, but constructor is preferable if you need an immutable contact).

cklab Over a year ago

Updated a bit, hopefully that helps a bit :)

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