如何与它的数据集的指数RecyclerView适配器的位置？ [英] How is the position of a RecyclerView adapter related to the index of its dataset?

问题描述

我以为他们是一样的，但他们没有。下面code给出了一个例外indexOutOfBounds当我尝试访问我的数据集的位置的索引，在这种情况下，一个模式，我创建了名为任务的列表：

I thought they were the same, but they're not. The following code gives an indexOutOfBounds exception when I try to access the "position" index of my dataset, in this case a list of a model I created called Task:

public class TaskAdapter extends RecyclerView.Adapter<TaskAdapter.TaskViewHolder>   {

private List<Task> taskList;
private TaskAdapter thisAdapter = this;

// cache of views to reduce number of findViewById calls
public static class TaskViewHolder extends RecyclerView.ViewHolder {
    protected TextView taskTV;
    protected ImageView closeBtn;

    public TaskViewHolder(View v) {
        super(v);
        taskTV = (TextView)v.findViewById(R.id.taskDesc);
        closeBtn = (ImageView)v.findViewById(R.id.xImg);
    }
}


public TaskAdapter(List<Task> tasks) {
    if(tasks == null)
        throw new IllegalArgumentException("tasks cannot be null");
    taskList = tasks;
}


// onBindViewHolder binds a model to a viewholder
@Override
public void onBindViewHolder(TaskViewHolder taskViewHolder, int pos) {
    final int position = pos;
    Task currTask = taskList.get(pos);
    taskViewHolder.taskTV.setText(currTask.getDescription());

    **taskViewHolder.closeBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Log.d("TRACE", "Closing task at position " + position);
            // delete from SQLite DB
            Task taskToDel = taskList.get(position);
            taskToDel.delete();
            // updating UI
            taskList.remove(position);
            thisAdapter.notifyItemRemoved(position);
        }
    });**
}

@Override
public int getItemCount() {
    //Log.d("TRACE", taskList.size() + " tasks in DB");
    return taskList.size();
}


// inflates row to create a viewHolder
@Override
public TaskViewHolder onCreateViewHolder(ViewGroup parent, int pos) {
    View itemView = LayoutInflater.from(parent.getContext()).
                                   inflate(R.layout.list_item, parent, false);
    Task currTask = taskList.get(pos);

    //itemView.setBackgroundColor(Color.parseColor(currTask.getColor()));
    return new TaskViewHolder(itemView);
}
}

从我recyclerview删除给出了意想不到的效果，有时。有时提前一个的元件点击被删除，其它时候一个indexOutOfBounds异常在发生taskList.get（位置）。

Deleting from my recyclerview gives unexpected results sometimes. Sometimes the element ahead of the one clicked is deleted, other times an indexOutOfBounds exception occurs at "taskList.get(position)".

阅读的https://developer.android.com/reference/android/support/v7/widget/RecyclerView.Adapter.html和 https://developer.android.com/training/material/lists-cards。 HTML 没有给我任何更深入地了解为什么这发生，以及如何解决它。

Reading https://developer.android.com/reference/android/support/v7/widget/RecyclerView.Adapter.html and https://developer.android.com/training/material/lists-cards.html did not give me any more insight into why this was happening and how to fix it.

它看起来像RecyclerView回收行，但使用的数字一个较小的子索引我的名单我不希望一个indexoutofbounds例外。

It looks like RecyclerView recycles the rows, but I wouldn't expect an indexoutofbounds exception using a smaller subset of numbers to index my list.

推荐答案

你为什么不使用公用接口按钮点击CONTROLE在MainActivity的动作。

Why dont you use a public interface for the button click and controle the action in the MainActivity.

在您添加适配器：

public interface OnItemClickListener {
    void onItemClick(View view, int position, List<Task> mTaskList);
}

和

public OnItemClickListener mItemClickListener;

// Provide a suitable constructor (depends on the kind of dataset)
public TaskAdapter (List<Task> myDataset, OnItemClickListener mItemClickListener) {
    this.mItemClickListener = mItemClickListener;
    this.mDataset = mDataset;
}

加上在ViewHolder类呼叫

plus the call in the ViewHolder class

 public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

    public ViewHolder(View v) {
        super(v);
        ...
        closeBtn = (ImageView)v.findViewById(R.id.xImg);
        closeBtn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        // If not long clicked, pass last variable as false.
        mItemClickListener.onItemClick(v, getAdapterPosition(), mDataset);
    }
}

在您MainActivity更改适配器处理呼叫

In your MainActivity change your adapter to handle the call

// set Adapter
    mAdapter = new TaskAdapter(taskList, new TaskAdapter.OnItemClickListener() {

        @Override
        public void onItemClick(View v, int position) {
            if (v.getId() == R.id.xImg) {
                Task taskToDel = taskList.get(position);
                // updating UI
                taskList.remove(position);
                thisAdapter.notifyItemRemoved(position);
                // remove from db with unique id to use delete query
                // dont use the position but something like taskToDel.getId() 
                taskToDel.delete();
            } 
        }
    });

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