Android Studio从回收站视图和列表中删除项目 [英] Android Studio Delete Items from Recycler View and List
问题描述
当我单击某个特定项目时,我正尝试将其删除.我已经运行了日志,所以我知道它正在选择一个项目,我只是不明白错误的含义.如果重要的话,我正在使用会议室数据库并使用回收站视图.
I am trying to remove a specific item when I click on it. I have run logs so I know that it's picking an item I just don't understand what the error means. If it is important I am using room database and using a recycler view.
java.lang.NullPointerException:尝试调用虚拟方法'voiduk.edu.le.co2103.myrecipebook.RecipeListAdapter.notifyItemRemoved(int)'在空对象上参考在uk.edu.le.co2103.myrecipebook.MainActivity $ 4.onClick(MainActivity.java:126)
java.lang.NullPointerException: Attempt to invoke virtual method 'void uk.edu.le.co2103.myrecipebook.RecipeListAdapter.notifyItemRemoved(int)' on a null object reference at uk.edu.le.co2103.myrecipebook.MainActivity$4.onClick(MainActivity.java:126)
我检查了列表中是否有数据,因此检查了以下日志.
I have checked that there is data in the list hence the logs below.
D/主要活动:列表:[uk.edu.le.co2103.myrecipebook.Recipe@c97e34d,uk.edu.le.co2103.myrecipebook.Recipe@e7b6e02,uk.edu.le.co2103.myrecipebook.Recipe@ d9ea313]2020-04-01 23:07:29.300 25679-25679/uk.edu.le.co2103.myrecipebook D/主要活动:索引:2
D/MAIN ACTIVITY: List: [uk.edu.le.co2103.myrecipebook.Recipe@c97e34d, uk.edu.le.co2103.myrecipebook.Recipe@e7b6e02, uk.edu.le.co2103.myrecipebook.Recipe@d9ea313] 2020-04-01 23:07:29.300 25679-25679/uk.edu.le.co2103.myrecipebook D/MAIN ACTIVITY: Index: 2
这是主要活动中我删除部分的代码
Here is the code for my deletion part of main Activity
public void onItemClick(int position, View view) {
Log.d(TAG, "onItemClick Position: " + position);
AlertDialog.Builder alertDialog = new AlertDialog.Builder(this);
alertDialog.setTitle("Edit or Delete...");
alertDialog.setPositiveButton("Edit", new
DialogInterface.OnClickListener()
alertDialog.setNegativeButton("Delete", new
DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
//Delete
Log.d(TAG, "List: " + recipesList);
Log.d(TAG, "Index: " + position);
int removeIndex = position;
recipesList.remove(removeIndex);
mAdapter.notifyItemRemoved(removeIndex);
}
});
我的适配器代码
public class RecipeListAdapter extends
RecyclerView.Adapter<RecipeListAdapter.RecipeViewHolder> {
private OnItemClickListener mListener;
private LiveData<List<Recipe>> recipeList;
public interface OnItemClickListener{
void onItemClick(int position, View view);
}
public void setOnItemClickListener(OnItemClickListener listener){
mListener = listener;
}
class RecipeViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
private final TextView recipeItemView;
private RecipeViewHolder(View itemView) {
super(itemView);
recipeItemView = itemView.findViewById(R.id.textView);
itemView.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
if (mListener != null){
int position = getAdapterPosition();
if (position != RecyclerView.NO_POSITION){
mListener.onItemClick(position, v);
}
}
}
});
}
@Override
public void onClick(View view) {
mListener.onItemClick(getAdapterPosition(), view);
}
}
private final LayoutInflater mInflater;
private List<Recipe> mRecipes; // Cached copy of words
RecipeListAdapter(Context context) {
mInflater = LayoutInflater.from(context);
this.recipeList = recipeList;
}
@Override
public RecipeViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = mInflater.inflate(R.layout.recyclerview_item, parent, false);
return new RecipeViewHolder(itemView);
}
@Override
public void onBindViewHolder(RecipeViewHolder holder, int position) {
if (mRecipes != null) {
Recipe current = mRecipes.get(position);
holder.recipeItemView.setText(current.getName());
} else {
// Covers the case of data not being ready yet.
holder.recipeItemView.setText("No Recipes");
}
}
void setWords(List<Recipe> recipes){
mRecipes = recipes;
notifyDataSetChanged();
}
// getItemCount() is called many times, and when it is first called,
// mWords has not been updated (means initially, it's null, and we can't return null).
@Override
public int getItemCount() {
if (mRecipes != null)
return mRecipes.size();
else return 0;
}
public interface OnNoteListener{}
}
推荐答案
我认为您没有初始化适配器或列表.
I think you didn't initialize the adapter or the list.
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