Android应用开发|自定义BaseAdapter无法正常工作

Question

我正在制作一个计划应用程序，每周都有相同的任务。我首先使用ArrayAdapter来显示所选日期的所有任务，但后来我决定制作自己的适配器。我从来没有制作过一个，所以我在互联网上看，然后通过大多数复制粘贴和更改变量来制作我的。当我在EditActivity中添加任务时，您可以看到它，但是当您切换所选日期并返回时，或者如果您转到DisplayActivity，它就会消失。没有错误。我也尝试过实现Filterable，但我也不知道它是什么，所以我主要是复制粘贴。

TaskAdapter

public class TaskAdapter extends BaseAdapter /*implements Filterable*/ {
private HashMap<Task, ViewHolder> holders = new HashMap<>();
private List<Task> mData = new ArrayList<>();
private LayoutInflater mInflater;

public TaskAdapter(Context context, List<Task> tasks) {
    mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    mData = tasks;
    holders = new HashMap<>();
    for (Task task : tasks) {
        if (holders.containsKey(task))
            return;
        ViewHolder holder = new ViewHolder();
        View convertView = mInflater.inflate(R.layout.list_item, null);
        holder.textView = (TextView) convertView.findViewById(R.id.list_item_text);
        convertView.setTag(holder);
        holders.put(task, holder);
    }
}

public void addItem(final Task task) {
    mData.add(task);
    notifyDataSetChanged();
    if (holders.containsKey(task))
        return;
    ViewHolder holder = new ViewHolder();
    View convertView = mInflater.inflate(R.layout.list_item, null);
    holder.textView = (TextView) convertView.findViewById(R.id.list_item_text);
    convertView.setTag(holder);
    holders.put(task, holder);
}

public void removeItem(final Task task) {
    mData.remove(task);
    holders.remove(task);
}

public void setItem(int position, Task task) {
    mData.set(position, task);
}

@Override
public int getCount() {
    return mData.size();
}

@Override
public Task getItem(int position) {
    return mData.get(position);
}

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder;
    if (convertView == null) {
        holder = new ViewHolder();
        convertView = mInflater.inflate(R.layout.list_item, null);
        holder.textView = (TextView) convertView.findViewById(R.id.list_item_text);
        convertView.setTag(holder);

    } else {
        holder = (ViewHolder) convertView.getTag();
    }
    holder.textView.setText(mData.get(position).getTask());
    return convertView;
}

public TextView getTextView(Task task) {
    return holders.get(task).textView;
}

/*
@Override
public Filter getFilter() {
    return new Filter() {

        @Override
        protected void publishResults(CharSequence constraint,
                                      FilterResults results) {
            mData = (List<Task>) results.values;
            TaskAdapter.this.notifyDataSetChanged();
        }

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {

            List<Task> filteredResults = getFilteredResults(constraint);

            FilterResults results = new FilterResults();

            results.values = filteredResults;

            return results;
        }
    };
} */

public static class ViewHolder {
    public TextView textView;
}

}

EditActivity - onCreate（）

if (getIntent().getExtras() != null) {
        selectedDay = getIntent().getExtras().getString("DAY");

        List<Task> tasks = getTasks(selectedDay);
        tasks.add(new Task(this, getIntent().getExtras().getString("TASK_NAME"), false, true));
        setTasks(selectedDay, tasks);
        updateList(tasks);
    }

EditActivity - setTasks（String day）

    private void setTasks(String day, List<Task> tasks) {
    try {
        FileOutputStream fileOutputStream = openFileOutput(day + ".dat", MODE_PRIVATE);
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream);
        objectOutputStream.writeObject(tasks);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

EditActivity - updateList（）

    private void updateList(List<Task> tasks) {
    if (tasks.size() == 0) {
        noPlanTextView.setVisibility(View.VISIBLE);
    } else {
        noPlanTextView.setVisibility(View.INVISIBLE);
    }
    TaskAdapter adapter = new TaskAdapter(this, tasks);
    adapter.notifyDataSetChanged();
    ListView listView = (ListView) findViewById(R.id.listview_edit);
    listView.setAdapter(adapter);
}

我只粘贴了我认为重要/有用的代码。如果您还想要，请告诉我。谢谢！