如何删除ArrayList的项目，然后更新列表视图 [英] How to remove arraylist item and then update listview

问题描述

ListView listView;
Activity activity;
public ArrayList<Tasks> tasks;
View v;

public TaskAdapter(Activity activity, ArrayList<Tasks> tasks)
{
    super(activity, R.layout.presenterlayout, tasks);
    this.activity = activity;
    this.tasks = tasks;
}

static class ViewHolder {
    public TextView taskTitleTextView;
    public TextView taskDescriptionTextView;
    public TextView taskDueTimeTextView;
    public CheckBox checkBox;
}

public View getView(final int position, View convertView, ViewGroup parent) {
    final ViewHolder holder;
    v = convertView;
    if (v == null) {
        LayoutInflater inflator = activity.getLayoutInflater();
        v = inflator.inflate(R.layout.presenterlayout, null, false);
        listView = (ListView) v.findViewById(R.id.listView);
        holder = new ViewHolder();
        holder.taskTitleTextView = (TextView)      v.findViewById(R.id.taskTitleTextView);
        holder.taskDescriptionTextView = (TextView) v.findViewById(R.id.taskDescriptionTextView);
        holder.taskDueTimeTextView = (TextView) v.findViewById(R.id.taskDueTimeTextView);
        holder.checkBox = (CheckBox) v.findViewById(R.id.checkBox);
        holder.taskTitleTextView.setText(tasks.get(position).getTasksTitleString());
        holder.taskDescriptionTextView.setText(tasks.get(position).getTasksDescriptionString());
        holder.taskDueTimeTextView.setText(tasks.get(position).getTasksDueTimeString());
        holder.checkBox.setId(position);
        holder.checkBox.setOnCheckedChangeListener(new OnCheckedChangeListener() {

            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if(holder.checkBox.isChecked())
                {
                    System.out.println("postion: " + position);
                    if(tasks.get(position).isTasksCompleted().equals("true"))
                    {
                        tasks.get(position).setTasksCompleted("false");                         
                    }
                    else if(tasks.get(position).isTasksCompleted().equals("false"))
                    {
                        tasks.get(position).setTasksCompleted("true");                          
                    }
                    updateThisTask(tasks.get(position));
                    tasks.remove(position);
                    notifyDataSetChanged();
                }
            }
        });
    }
    else {
        v = convertView;
    }
    return v;
}

private void updateThisTask(Tasks tasks) {
    DBAdapter dbAdapter = new DBAdapter(getContext());
    int id = dbAdapter.getID(tasks);
    dbAdapter.updateTask(tasks, id);
}

}

我想从数组列表中删除项。正如你可以看到我使用复选框。我第一次点击复选框，正确的项目被删除。如果我点击复选框第二次，应用程序崩溃是由于索引越界。我怎样才能把所谓的任务数组列表中的项目，并更新列表视图？

I want to remove item from the array list. As you can see I am using checkbox. The first time I click the checkbox, correct item is removed. The second time if I click the checkbox, the application crashes due to index out of bounds. How can I remove an item from the array list called tasks and update the listview?

推荐答案

在您从任务删除项目阵列，所有以后的项目中取得了新的索引因此，所有的的位置，你已经保存在持有人，并传递给值 OnCheckedChangeListener 是错误的。我fyou想这样做这样一来，你不能依赖于使用数组作为查找条目的方式中的位置。你需要使用对象本身和搜索数组找到匹配的对象。使用类似

Once you remove an item from the tasks array, all of the items after that get a new index so all of the position values that you've saved in the holders and passed to the OnCheckedChangeListener are wrong. I fyou want to do this this way, you can't rely on using the position in the array as a way of finding an entry. You'll need to use the object itself and search the array to find the matching object. Use something like

int arrayIndexOfThisTask = tasks.indexOf(objectThatIsInTheArray);

编辑：添加code例如：

试试这个：

public View getView(int position, View convertView, ViewGroup parent) {
    final ViewHolder holder;
    v = convertView;
    if (v == null) {
        LayoutInflater inflator = activity.getLayoutInflater();
        v = inflator.inflate(R.layout.presenterlayout, null, false);
        listView = (ListView) v.findViewById(R.id.listView);
        holder = new ViewHolder();
        v.setTag(holder); // Attach the holder to the view so we can find it again
        holder.taskTitleTextView = (TextView)      v.findViewById(R.id.taskTitleTextView);
        holder.taskDescriptionTextView = (TextView) v.findViewById(R.id.taskDescriptionTextView);
        holder.taskDueTimeTextView = (TextView) v.findViewById(R.id.taskDueTimeTextView);
        holder.checkBox = (CheckBox) v.findViewById(R.id.checkBox);
    } else {
        // Get the ViewHolder from the recycled view
        holder = (ViewHolder)v.getTag();
    }
    // Get the task at this position in the array
    final Task task = tasks.get(position);

    holder.taskTitleTextView.setText(task.getTasksTitleString());
    holder.taskDescriptionTextView.setText(task.getTasksDescriptionString());
    holder.taskDueTimeTextView.setText(task.getTasksDueTimeString());
    holder.checkBox.setOnCheckedChangeListener(new OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            if(holder.checkBox.isChecked())
            {
                // Try to find the position in the array for this object (it may already have been removed)
                int position = tasks.indexOf(task);
                System.out.println("postion: " + position);
                // If this object is no longer in the array, just ignore this action
                if (position >= 0) {
                    if(tasks.get(position).isTasksCompleted().equals("true"))
                    {
                        tasks.get(position).setTasksCompleted("false");                         
                    }
                    else if(tasks.get(position).isTasksCompleted().equals("false"))
                    {
                        tasks.get(position).setTasksCompleted("true");                          
                    }
                    updateThisTask(tasks.get(position));
                    tasks.remove(position);
                    notifyDataSetChanged();
                }
            }
        }
    });
    return v;
}

我可能没有一切完全正确的，但你应该明白了吧。

I may not have everything exactly right, but you should get the idea.

有实际上许多事情不对您的code：

There were actually many things wrong with your code:

1. 您没有正确使用 ViewHolder 模式。你永远不使用 setTag（）附 ViewHolder 到查看本身，你永远不检索 ViewHolder 从查看给出 convertView 。


2. 如果 convertView 是非空你刚回到它没有做任何事的。这是错误的，因为适配器回收认为它想要的任何方式，它可以通过你的查看 6的位置，并要求查看的位置1。在这种情况下，您刚刚返回的查看为第6位（这是不正确的）。


3. 我已经通过实际的工作对象到 onCheckChanged（）方法，而不是传递的位置和我的以前用过的indexOf（）来获取数组该对象的当前位置。

1. You weren't using the ViewHolder pattern correctly. You never attached the ViewHolder to the View itself by using setTag() and you never retrieved the ViewHolder from the View when given a recycled view in convertView.
2. If convertView was non-null you just returned it without doing anything with it. This is wrong because the adapter recycles views any way it wants to and it may pass you the View from position 6 and ask for a View for position 1. In this case you would have just returned the View for position 6 (which isn't correct).
3. I've passed the actual Task object into the onCheckChanged() method instead of passing the position and I've used indexOf() to get the current position in the array for that object.

我希望这是很有帮助的。

I hope this is helpful.

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