ListView

Question

我想在我的Android应用程序的ListView中添加每个项目的子项。为此我写了这段代码（如下所示）。但这不起作用。我是Android的新手，我已经看到很多解决这个问题的例子，但他们没有帮助。因此，请告诉我如何在ListView中添加每个项目的子项目。

ListDisplay.java

public class ListDisplay extends AppCompatActivity {

    String[] items = {"Android","IPhone","WindowsMobile","Blackberry","WebOS","Ubuntu","Windows7","Max OS X"};
    String[] subItems = {"lollipop","4s","8.1","a1","os","ubnt","7","air"};

    public static ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list_display);

        listView = (ListView) findViewById(R.id.listViewItems);
        ArrayAdapter adapter = new ArrayAdapter<String>(context, R.layout.activity_listview, items, subItems);
        ListDisplay.listView.setAdapter(adapter);
    }

}

activity_listview.xml

<?xml version="1.0" encoding="utf-8"?>
<!--  Single List Item Design -->

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/label"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dip"
    android:textSize="16dip"
    android:textStyle="bold" >
</TextView>

content_list_display.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.abc.project1.ListDisplay"
    tools:showIn="@layout/activity_list_display">

    <ListView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/listViewItems"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_alignParentTop="true" />
</RelativeLayout>

Answer 1

您需要为此制作自定义适配器。这是您应该使用的代码。

/** class to act as list adapter for rows List */
private static class TwoTextListAdapter extends ArrayAdapter<MyDataClass> {

    /** To cache views of item */
    private static class ViewHolder {
        private TextView label;
        private TextView subLabel;

        /**
         * General constructor
         */
        ViewHolder() {
            // nothing to do here
        }
    }

    /** Inflater for list items */
    private final LayoutInflater inflater;

    /**
     * General constructor
     *
     * @param context
     * @param resource
     * @param textViewResourceId
     * @param objects
     */
    public TwoTextListAdapter(final Context context,
            final int resource,
            final int textViewResourceId,
            final List<User> objects) {
        super(context, resource, textViewResourceId, objects);

        this.inflater = LayoutInflater.from(context);
    }

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

        View itemView = convertView;
        ViewHolder holder = null;
        final MyDataClass item = getItem(position);

        if(null == itemView) {
            itemView = this.inflater.inflate(R.layout.activity_listviewpar, parent, false);

            holder = new ViewHolder();

            holder.label = (TextView)itemView.findViewById(R.id.label);
            holder.subLabel = (TextView)itemView.findViewById(R.id.subLabel);

            itemView.setTag(holder);
        } else {
            holder = (ViewHolder)itemView.getTag();
        }

        holder.label.setText(item.getlabel());
        holder.subLabel.setText(item.getsubLabel());

        return itemView;
    }
}

activity_listview.xml应该如下所示

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/label"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dip"
    android:textSize="16dip"
    android:textStyle="bold" >
</TextView>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/subLabel"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dip"
    android:textSize="16dip"
    android:textStyle="bold" >
</TextView>
</LinearLayout>

最后在ListDisplay中执行此操作

public class ListDisplay extends AppCompatActivity {

    String[] items = {"Android","IPhone","WindowsMobile","Blackberry","WebOS","Ubuntu","Windows7","Max OS X"};
    String[] subItems = {"lollipop","4s","8.1","a1","os","ubnt","7","air"};

    public static ListView listView;
    public List<Item> list = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list_display);

        for(int i=0;i<items.length;i++){
            list.add(new Item(items[i],subItems[i]))
        }

        listView = (ListView) findViewById(R.id.listViewItems);
        TwoTextListAdapter adapter = new TwoTextListAdapter(context, R.layout.activity_listview, null, list);
        ListDisplay.listView.setAdapter(adapter);
    }

    public class Item {
        public String a,b;

        public Item(String a, String b) {
            this.a = a;
            this.b = b;
        }
    }

}