哈希图并从中检索数据

Question

I've to do an action on more item of my listview so i create an HashMap with the name of selected application (in my list) and relative position.

public void createHashMap(String name, int mPosition) {
    // TODO Auto-generated method stub
    mHashMap = new HashMap<String, Integer>();
    mHashMap.put(name, mPosition);
    Toast.makeText(context, name+": "+mPosition, Toast.LENGTH_LONG).show();

}

in onItemClick of my activity class

        adapter.createHashMap(itemName, mPosition);

So, when i click on a row i show the toast with the correct information now i've need to retrieve the data into hashmap and i wrote this

public void retrieveHashMap() {
    Iterator myVeryOwnIterator = mHashMap.keySet().iterator();
    while(myVeryOwnIterator.hasNext()) {
        String key=(String)myVeryOwnIterator.next();
        int value= mHashMap.get(key);
        Toast.makeText(context, "Key: "+key+" Value: "+value, Toast.LENGTH_LONG).show();
    }

}

This work but when i call retrieveHashMap method i show ONLY the last insert value. How can i show ALL the inserted value??

Answer 1

Move Toast.makeText outside the while loop and create the message you want inside the loop using the keys you iterate over.

You also need to check if you override existing mHashMap in createHashMap()

Answer 2

Look like your problem is that you initialize new hash map every time. That's why you got only the last value. Try this:

 public void createHashMap(String name, int mPosition) {
// init it only one time.
if(mHashMap  == null){
    mHashMap = new HashMap<String, Integer>();
}
mHashMap.put(name, mPosition);
Toast.makeText(context, name+": "+mPosition, Toast.LENGTH_LONG).show();

}

And the toast has a duration time, so you shouldn't call it many times. If you try write log, you should use logcat.

Update: another reason, maybe your data has duplicate the name value. Try to debug or write to logcat and see if you have insert many name data have the same value. Because the hash map is not accepted the duplicate key. For example:

  mHashMap.put("test", 2);
  mHashMap.put("test", 3); // it will replace the item ["test" - 2] by ["test" - 3]. That's why you got only the last one. 

And make sure your iterator should look like this:

 Iterator<String> myVeryOwnIterator = mHashMap.keySet().iterator();
    while(myVeryOwnIterator.hasNext()) {
        String key=(String)myVeryOwnIterator.next();
        int value= mHashMap.get(key);
        System.out.println(key + " " + value);
    }

Hope this help!

Answer 3

When you use this method

public void createHashMap(String name, int mPosition) {
// TODO Auto-generated method stub
mHashMap = new HashMap<String, Integer>();
mHashMap.put(name, mPosition);
Toast.makeText(context, name+": "+mPosition, Toast.LENGTH_LONG).show();

}

you have to save hashmap or toast instance. when call

 mHashMap = new HashMap<String, Integer>();

and call

Toast.makeText(context, name+": "+mPosition, Toast.LENGTH_LONG).show();

refreshed(create again) all data in instance.

Answer 4

It looks like you are reseting mHashMap every time the method createHashMap is called: mHashMap = new HashMap();

Instead, you should have this only where you declare mHashMap (as a class member) and then in createHashMap only have the "mHashMap.put(name, mPosition)" part.