Question

首先，我尝试使用随机数据填充FrgamentList，但列表始终为空。还尝试使用ListView切换到片段，但它也不起作用。这是我的项目代码：

activity_main.xml中：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <fragment
        android:id="@+id/fragment1"
        android:name="as400samplecode.com.myapplication.MyListFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

fragment_item.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >

    <ImageView
        android:id="@+id/placeImage"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:padding="5dp" />

    <LinearLayout android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:id="@+id/placeName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Medium Text"
            android:textAppearance="?android:attr/textAppearanceMedium"
            android:layout_marginLeft="10dp"
            android:layout_marginTop="5dp"
            android:padding="2dp" />
    </LinearLayout>
</LinearLayout>

list_fragment.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ListView>

    <TextView
        android:id="@android:id/empty"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </TextView>

</LinearLayout>

位置：

public class Location {
    public String locName;
    public int locImage;

    public Location(String locName, int locImage) {
        this.locName = locName;
        this.locImage = locImage;
    }
}

MainActivity：

public class MainActivity extends Activity {

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

MyListFragment：

    public class MyListFragment extends ListFragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.list_fragment, container, false);

        return view;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {

        super.onActivityCreated(savedInstanceState);

        List<Location> locations = new ArrayList<>();
        locations.add(new Location("bla5", R.drawable.eiffel));
        locations.add(new Location("bla6", R.drawable.eiffel));

        CustomListAdapter adapter = new CustomListAdapter(getActivity(), locations);

        setListAdapter(adapter);
    }
}

CustomListAdapter：

    public class CustomListAdapter extends ArrayAdapter<String> {

    private final Activity context;
    private List<Location> locations;

    public CustomListAdapter(Activity context, List<Location> locations) {
        super(context, R.layout.fragment_item);
        this.context = context;
        this.locations = locations;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        ViewHolder holder; // to reference the child views for later actions

        if (v == null) {
            LayoutInflater vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            v = vi.inflate(R.layout.fragment_item, null);
            // cache view fields into the holder
            holder = new ViewHolder();
            holder.imageView = (ImageView) v.findViewById(R.id.placeImage);
            holder.txtTitle = (TextView) v.findViewById(R.id.placeName);

            holder.txtTitle.setText(locations.get(position).locName);
            //holder.imageView.setImageBitmap(locations.get(position).locImage);
            holder.imageView.setImageResource(locations.get(position).locImage);

            // associate the holder with the view for later lookup
            v.setTag(holder);
        }

        return v;
    }

    static class ViewHolder {
        TextView txtTitle;
        ImageView imageView;
    }
}

知道它可以是什么吗？

谢谢！

Answer 1

问题在于此方法

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View v = convertView;
    ViewHolder holder; // to reference the child views for later actions

    if (v == null) {
        LayoutInflater vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = vi.inflate(R.layout.fragment_item, null);
        // cache view fields into the holder
        holder = new ViewHolder();
        holder.imageView = (ImageView) v.findViewById(R.id.placeImage);
        holder.txtTitle = (TextView) v.findViewById(R.id.placeName);

        holder.txtTitle.setText(locations.get(position).locName);
        //holder.imageView.setImageBitmap(locations.get(position).locImage);
        holder.imageView.setImageResource(locations.get(position).locImage);

        // associate the holder with the view for later lookup
        v.setTag(holder);
    }
  // although you have added a ViewHolder it is not used once your view is generated
 // you are just instantiating convertView if it is null and not doing anything after that   

    return v;
}

当您的convertView不为null时添加其他条件并检索您添加的ViewHolder实例

else {
  holder = (ViewHolder) v.getTag();
}
 // now you would be feeding information to your `ImageView` and `TextView`

holder.txtTitle.setText(locations.get(position).locName);
holder.imageView.setImageBitmap(locations.get(position).locImage);

Answer 2

必须覆盖get getCount()方法：

@Override
public int getCount(){
    return locations != null ? locations.size() : 0;
}

带有自定义适配器的空片段列表

2 个答案: