如何在Android中更新ListView？

Question

I want to upgrade my ListView on clicks on it's elements with updated amount of buildings (and price in future). Now, the list only updated when app are re-launched.

onCreate:

Building[] buildings = {
                new Building(1, getString(R.string.mouse), 15, iMouses),
                new Building(2, getString(R.string.grandma), 100, iGrandmas),
                new Building(3, getString(R.string.farm), 500, iFarms),
                new Building(4, getString(R.string.factory), 3000, iFactories),
                new Building(5, getString(R.string.mine), 10000, iMines)
        };

        ListView lstBuildings = (ListView)findViewById(R.id.lstBuildings);

        final ArrayAdapter<Building> adapter = new ArrayAdapter<>(this,
                android.R.layout.simple_list_item_1, buildings);

        lstBuildings.setAdapter(adapter);

        lstBuildings.setOnItemClickListener(new AdapterView.OnItemClickListener(){
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position,
                                    long id){
                if (id+1 == 1) { //         Mouse
                    if ((int) fCats >= 15) {
                        fIncome = fIncome + 0.1f;
                        fCats = fCats - 15;
                        iMouses = iMouses + 1;
                        iBuildings = iBuildings + 1;

                        adapter.notifyDataSetChanged();
                    }

My building class:

class Building {
    private final int id;
    private final String name;
    private final double price;
    private final int number;

    public Building(int id, String name, double price, int number) {
        super();
        this.id = id;
        this.name = name;
        this.price = price;
        this.number = number;
    }

    @Override
    public String toString() {
        return this.id + ". " + this.name + " [" + (int)this.price + "] (" + this.number + ")";
    }
}

Thanks for any help and please give me some tricks for optimization for my code.

Answer 1

The solution is pretty simple:

adapter.notifyDataSetChanged()

Look at this:

if (id+1 == 1) { //         Mouse
                if ((int) fCats >= 15)
                    fIncome = fIncome + 0.1f;
                    fCats = fCats - 15;
                    iMouses = iMouses + 1;
                    iBuildings = iBuildings + 1;

                    adapter.notifyDataSetChanged();
                }

you are simply not updating the data of the adapter you are just setting some variables

Answer 2

First, I see you update the variable iMouses, but you do not update the location in the buildings array where you stored iMouses previously. So the data in the buildings array has not changed. It must change in the array as that is what is displayed in the listview.

Also, you will need to implement the following code to get notifyDataSetChanged to function. The data in the adapter is a different set that your buildings array.

adapter.clear();
adapter.addAll(buildings);
notifyOnDataSetChanged();