Question

我试图在我的应用中ListView中实施AlertDialog。

点击按钮后调用listDialog()：

public void listDialog() {
        LayoutInflater shoppingListInflater = LayoutInflater.from(this);
        final View allListsView = shoppingListInflater.inflate(R.layout.list_picker_dialog, null);

        listsPickerView = (ListView) findViewById(R.id.shopping_lists_all);

        shoppingLists = new ArrayList<ShoppingList>();

        allListsAdapter = new ShoppingListsAdapter(this, shoppingLists);

        listsPickerView.setAdapter(allListsAdapter);

        AlertDialog.Builder listsDialog = new AlertDialog.Builder(this);

        listsDialog.setView(allListsView);

        listsDialog.setCancelable(false)
                    .setNegativeButton("Cancel",
                            new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            dialog.cancel();
                        }
                    });

            AlertDialog alertD = listsDialog.create();

            alertD.show();

    }

在我的活动中，我有：

private ListView listsPickerView;
private ShoppingListsAdapter allListsAdapter;
private List<ShoppingList> shoppingLists;

我的适配器看起来像这样：

public class ShoppingListsAdapter extends BaseAdapter {  
    private Activity activity;
    private LayoutInflater inflater;
    private List<ShoppingList> shoppingLists;
    ImageLoader imageLoader = AppController.getInstance().getImageLoader();

    public ShoppingListsAdapter(Activity activity, List<ShoppingList> shoppingLists) {
        this.activity = activity;
        this.shoppingLists = shoppingLists;
    }

    @Override
    public int getCount() {
        return shoppingLists.size();
    }

    @Override
    public Object getItem(int location) {
        return shoppingLists.get(location);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        if (inflater == null)
            inflater = (LayoutInflater) activity
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (convertView == null)
            convertView = inflater.inflate(R.layout.shopping_list, null);

        if (imageLoader == null)
            imageLoader = AppController.getInstance().getImageLoader();

        TextView name = (TextView) convertView
                .findViewById(R.id.listName);
        TextView listCount = (TextView) convertView
                .findViewById(R.id.listCount);
        TextView list_id = (TextView) convertView
                .findViewById(R.id.list_id);


        ShoppingList sList = shoppingLists.get(position);

        // set list count
        listCount.setText(sList.getListCount());

        //set name
        name.setText(sList.getName());

        list_id.setText(String.valueOf(sList.getId()));

        return convertView;
    }

}

我的list_picker_dialog布局：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:background="#ffffff">

    <ListView
        android:id="@+id/shopping_lists_all"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:divider="@null"
        android:dividerHeight="1dp"
        android:cacheColorHint="#00000000"/>

</LinearLayout>

我在这一行获得了一个NPE：listsPickerView.setAdapter(allListsAdapter);方法listsDialog()。我在Dialog中实现ListView有什么问题吗？提前谢谢。

Answer 1

由于您的ListView可能位于AlertDialog的布局中，因此您需要在View为Dialog充气。像这样：

listsPickerView = (ListView) allListsView.findViewById(R.id.shopping_lists_all);

您获得NullPointerException的原因是因为您编写的代码正在ListView的{{1}}布局中搜索Activity，当它找不到时返回null。

AlertDialog中的Android ListView - 设置适配器

1 个答案: