Android MultiSelectListPreference的优先顺序

Question

I'm new to Android. I want to use MultiSelectListPreference for my case.

But I encounter a problem: My list need to keep the order of element. Assume there're 5 elements:

0 - Tom
1 - David
2 - Bob
3 - Mary
4 - Chris

and user choose 0, 2, 3. Then the list is must be in the order as below:

Tom, Bob, Mary

But the MultiSelectListPreference stores setting in Set<String> , not ArrayList<String> , so it's not sure for this order because of Set .

How can I make sure this order? Thank you.

Answer 1

camdaochemgio, I understood your question even before your edit.

Since we are talking about a Set (that stores unique values) , This getValues() function needs to be fed into your own revertValues function that translates the values into indexes - based on your preset of the data. I asked for your code so I could express myself by writing the solution to this in your own style/terminology.

The Solution:

I noticed in the docs of MultiSelectListPreference the following method :

int findIndexOfValue(String value)

But you do not store such reference to the object, So I created this class to extend MultiSelectListPreference (in new file!) :

public class DataHolder extends MultiSelectListPreference {

    // note: AttributeSet  is needed in super class
    public DataHolder(Context context,AttributeSet attrs) {   
        super(context, attrs);

        List<CharSequence> entries = new ArrayList<CharSequence>();
        List<CharSequence> entriesValues = new ArrayList<CharSequence>();

        /** We could use the String Array like you did in your Q, 
         * But I preffer this way of populating data - 
         * It keeps things open and unlimitted.
         * If you really want the data picked up from the xml , just use : 
         * context.getResources().getStringArray(R.array.entries)  and
         * context.getResources().getStringArray(R.array.entryValues) 
         * */

        entries.add("0");
        entries.add("1");
        entries.add("2");
        entries.add("3");
        entries.add("4");
        entriesValues.add("Tom");
        entriesValues.add("David");
        entriesValues.add("Bob");
        entriesValues.add("Mary");
        entriesValues.add("Chris");

        setEntries(entries.toArray(new CharSequence[5]));
        setEntryValues(entriesValues.toArray(new CharSequence[5]));
    }
}

Now we need to plug it in your listener. In your SettingsFragment class , just add a new field :

private DataHolder dh = null;

And change the constructor to accept it and initialize it :

public SettingsFragment(Context c) {
    dh = new DataHolder(c,null);
}

Next step: remove the reference to the data from the xml. It should look like this now :

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >
    <com.example.multiselectpref.DataHolder
        android:key="pref_key_name_choice"
        android:title="@string/name_choice"
    />
</PreferenceScreen>

Back to your listener, in onSharedPreferenceChanged method , You can change the toast to :

toast_message += (dh.findIndexOfValue(name) + ": "+name+"    , ");

Works for me.. (code committed to fork @ https://github.com/li3ro/MultiSelectPref )