java - 无法弄清楚为什么 fragment 中没有显示列表

Question

您好，我一直在尝试使用 fragment 和列表。由于某种原因，应用程序打开时不会显示列表。如果您能帮助我找到原因并解决它，我将不胜感激!我在很多网站上寻找答案，但仍然找不到合适的答案。

package androidarena.tab.Tabs;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.BaseAdapter;
import java.util.ArrayList;
import android.util.Log;
import androidarena.tab.R;

public class Assignments extends Fragment {

    ListView list;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View assignmentsV = inflater.inflate(R.layout.assignments_frag, container, false);
        ArrayList<AssignmentOBJ> items=new ArrayList<AssignmentOBJ>();
        for (int i =0; i<10; i++) {
            AssignmentOBJ item=new AssignmentOBJ("A "+i, "A "+i, "A "+i);
            items.add(item);
            Log.d("loop", "date: "+item.getDate());
        }

        AssignmentsListAdapter adapter=new AssignmentsListAdapter(getActivity(), items);
        list=(ListView) assignmentsV.findViewById(R.id.listView123);
        list.setAdapter(adapter);

        return assignmentsV;

    }

    public class AssignmentsListAdapter extends ArrayAdapter<AssignmentOBJ> {

        ArrayList<AssignmentOBJ> items;
        LayoutInflater layoutInflater;
        Activity context;

        public AssignmentsListAdapter(Activity context, ArrayList<AssignmentOBJ> items) {
            super(context, R.layout.assignments_row);
            this.items=items;
            this.context=context;
        }

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

            convertView= layoutInflater.inflate(R.layout.assignments_row, null, true);


            TextView txtTitle1 = (TextView) convertView.findViewById(R.id.textView2);
            TextView txtTitle2 = (TextView) convertView.findViewById(R.id.textView3);
            TextView txtTitle3 = (TextView) convertView.findViewById(R.id.textView4);

            txtTitle1.setText(items.get(position).getDate());

            txtTitle1.setText(items.get(position).getTopic());

            txtTitle1.setText(items.get(position).getSubject());

            return convertView;
        }

        @Override
        public long getItemId(int position) {
            return 0;
        }
    }

    private class AssignmentOBJ {
        String date;
        String topic;
        String subject;

        public AssignmentOBJ(String date, String topic, String subject) {
            this.date = date;
            topic = topic;
            subject = subject;
        }

        public String getDate() {
            return date;
        }

        public void setDate(String date) {
            this.date = date;
        }

        public String getSubject() {
            return subject;
        }

        public void setSubject(String subject) {
            subject = subject;
        }

        public String getTopic() {
            return topic;
        }

        public void setTopic(String topic) {
            topic = topic;
        }
    }
}

Answer 1

问题在这里:

public AssignmentsListAdapter(Activity context, ArrayList<AssignmentOBJ> items) {
        super(context, R.layout.assignments_row);
        this.items=items;
        this.context=context;
    }

您忘记将items传递给 super 构造函数。
只需更改为: super(context, R.layout.assignments_row, items);