Java 带有自定义适配器的空片段列表

首先，我试图用随机数据填充

FrgamentList

，但列表总是空的。 还尝试使用

ListView

切换到片段，但效果不佳。 这是我的项目代码：

activity_main.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" >

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

</LinearLayout>

主要活动：

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);
    }
}

公共类MyListFragment扩展ListFragment{
@凌驾
创建视图上的公共视图（布局、充气机、视图组容器、，
Bundle savedInstanceState）{
视图=充气机。充气（R.layout.list\u碎片，容器，错误）；
返回视图；
}
@凌驾
已创建ActivityState上的公共无效（Bundle savedInstanceState）{
super.onActivityCreated（savedInstanceState）；
列表位置=新的ArrayList（）；
位置。添加（新位置（“bla5”，R.drawable.eiffel））；
位置。添加（新位置（“bla6”，R.drawable.eiffel））；
CustomListAdapter=新的CustomListAdapter（getActivity（），位置）；
setListAdapter（适配器）；
}
}

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;
    }
}

公共类CustomListAdapter扩展了ArrayAdapter{
私人最终活动背景；
私人名单地点；
公共CustomListAdapter（活动上下文、列表位置）{
super（上下文、右布局、片段项）；
this.context=上下文；
这个位置=位置；
}
@凌驾
公共视图getView（int位置、视图转换视图、视图组父视图）{
视图v=转换视图；
ViewHolder；//为以后的操作引用子视图
如果（v==null）{
LayoutInflater vi=（LayoutInflater）context.getSystemService（context.LAYOUT\u INFLATER\u SERVICE）；
v=vi.充气（R.布局.碎片\项目，空）；
//将视图字段缓存到保持架中
holder=新的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））；
//将支架与视图关联，以便以后查找
v、 setTag（支架）；
}
返回v；
}
静态类视窗夹{
TextView-txtTitle；
图像视图图像视图；
}
}

知道会是什么吗

---

谢谢

问题在于这种方法

@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

不为空时，添加一个else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);

---

必须重写get

getCount（）

方法，如下所示：

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

---

这没用。一些非常奇怪的事情发生了，当我调试时，我看到应用程序从未达到那个方法，这正常吗？不，这不正常，看看几个自定义listview的例子，自定义适配器是如何工作的，试着把日志放在你认为检查代码进度所必需的地方

@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;
}

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);

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