安卓ListView适配器不会刷新

Question

我在使用自定义适配器刷新列表视图方面遇到了很多问题。我已经在线搜索了一个小时，但似乎找不到任何解决方案可以使我的列表视图刷新。

我尝试过使用 notifyDataSetChanged 和 listView.invalidate，但似乎没有什么作用。如能提供任何帮助将不胜感激。我可以在 logcat 中看到数据被更新，但屏幕上并未刷新，我也不知道原因。

以下是代码：

ArrayList<Student> students = new ArrayList<Student>();

listview = (ListView) findViewById(R.id.listView);
adapter = new StudentAdapter(this, R.layout.listitemlayout, students);  
listview.setAdapter(adapter);

自定义适配器

public class StudentAdapter extends ArrayAdapter<Student>{

    Context context; 
    int layoutResourceId;    
    ArrayList<Student> data = null;

    public StudentAdapter(Context context, int layoutResourceId, ArrayList<Student> data) {
        super(context, layoutResourceId, data);
        this.layoutResourceId = layoutResourceId;
        this.context = context;
        this.data = data;
    }

    public void updateStudentsList(ArrayList<Student> newlist){
        data.clear();
        data = newlist;
        this.notifyDataSetChanged();
    }

    public void updateStudentTime(){
        for (Student s : data) {
            s.updateElapsedTime();          
        }
        this.notifyDataSetChanged();
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;
        if(row == null){
            LayoutInflater inflater = ((Activity)context).getLayoutInflater();
            row = inflater.inflate(layoutResourceId, parent, false);

            Student student = data.get(position);

            TextView title = (TextView)row.findViewById(R.id.txtTitle);
            title.setText(student.getFirstname() + " " + student.getLastname());

            TextView subTitle = (TextView)row.findViewById(R.id.txtSubTitle);
            subTitle.setText(student.getStudentID());       

            TextView duration = (TextView)row.findViewById(R.id.textDuration);
            duration.setText(student.getElapsedTime());
        }
        return row;
    }
}

我会定期使用线程更新数据。

Runnable runnable = new Runnable() {
            public void run() {
                runOnUiThread(new Runnable() {
                    public void run() {
                        // Updates how long the student is in the centre.
                        adapter.updateStudentTime();
                        adapter.notifyDataSetChanged();
                        listview.invalidate();
                        Log.i("Debug", "Running on UI Thread");
                    }
                });
                handler.postDelayed(this, 1000);
            }
        };
        handler.postDelayed(runnable, 1000);

- SikhWarrior

---

在UI线程上更新UI。调用adapter.updateStudentTime(); 使用runOnUiThread。 - Raghunandan

Answer 1

ListView会回收视图，因此必须在getView中设置数据。 如果f(row == null){，意味着数据不会刷新，只使用旧数据。

你应该这样做：

Class ViewHolder {
   TextView title;
   TextView subTitle;
   TextView duration;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View row = convertView;
    ViewHolder holder = null;
    if(row == null){
        LayoutInflater inflater = ((Activity)context).getLayoutInflater();
        row = inflater.inflate(layoutResourceId, parent, false);

        Student student = data.get(position);
        holder = new ViewHolder();
        holder.title = (TextView)row.findViewById(R.id.txtTitle);
        holder.subTitle = (TextView)row.findViewById(R.id.txtSubTitle);
        holder.duration = (TextView)row.findViewById(R.id.textDuration);
        row.setTag(holder);
    } else {
        holder = row.getTag();
    }
    holder.title.setText(student.getFirstname() + " " + student.getLastname());
    holder.subTitle.setText(student.getStudentID());   
    holder.duration.setText(student.getElapsedTime());    
    return row;
}

- buptcoder

Answer 2

认为下面的代码可以防止您刷新列表。

if(row == null){    
...
}

代码中指出，当列表刷新时，它将检查行是否为空（即屏幕上显示的行是否已创建）。当您刷新列表时，该行已经被创建。因此它不是NULL，新数据将不会被设置！

您应该做出类似以下的更改：

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

    View row = convertView;

    if(row == null){
        LayoutInflater inflater = ((Activity)context).getLayoutInflater();
        row = inflater.inflate(layoutResourceId, parent, false);

    } 

    Student student = data.get(position);
    ...

}

- quantm