删除所有recyclerview项目后，TextView将不会显示 [英] TextView won't display after removing all recyclerview items
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问题描述
我已经实现了两个RecyclerView适配器，一个是RecyclerViewAdapter，另一个是EmptyRecyclerViewAdapter.我想做的是每当所有项目都被删除时，显示文本此处为空文本！.
I've implemented two RecyclerView adapters, one is RecyclerViewAdapter and the other one is EmptyRecyclerViewAdapter. What I'm trying to do is to display the text Empty Text Here! whenever all the items are removed.
图像2 将正常工作，它将显示文本此处为空文本！，该图像显示在图像2 ，但是，如果列表中已经有项目，并且如果我将删除列表中的所有项目，则 Image 1 将是不显示任何内容，不显示任何文本的结果.
Image 2 is working if there are no items yet in the list and it will display the text Empty Text Here! which is shown on Image 2 below however, If there are already items on the list and If i will remove all of the items in the list, Image 1 will be the result which displays nothing, no text.
EmptyRecyclerViewAdapter.class
EmptyRecyclerViewAdapter.class
public class EmptyRecyclerViewAdapter extends RecyclerView.Adapter<EmptyRecyclerViewAdapter.ViewHolder> {
private String mMessage;
public EmptyRecyclerViewAdapter(){}
public EmptyRecyclerViewAdapter(String message){ mMessage = message;}
@Override
public EmptyRecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.empty_item, parent, false);
ViewHolder viewHolder = new ViewHolder(view);
if(mMessage != null){
viewHolder.mMessageView.setText(mMessage);
}
return viewHolder;
}
@Override
public void onBindViewHolder(EmptyRecyclerViewAdapter.ViewHolder holder, int position) {}
@Override
public int getItemCount() { return 1; }
public class ViewHolder extends RecyclerView.ViewHolder {
final View mView;
final TextView mMessageView;
public ViewHolder(View view) {
super(view);
mView = view;
mMessageView = (TextView) view.findViewById(R.id.empty_item_message);
}
}
}
RecyclerViewAdapter.class
RecyclerViewAdapter.class
public class RecyclerViewAdapter extends RecyclerView.Adapter <RecyclerView.ViewHolder> {
private List<ItemModel> list;
private Context mContext = null;
public RecyclerViewAdapter (Context context, List<ItemModel> itemList) {
mContext = context;
this.list = itemList;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
return new MyViewHolder(view);
}
@Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, int position) {
final ItemModel l = list.get(holder.getAdapterPosition());
final DataDb dataDb = new DataDb (mContext);
((MyViewHolder) holder).title.setText(l.getTitle());
((MyViewHolder) holder).caption.setText(l.getCaption());
((MyViewHolder) holder).removeBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String confirmText = "Are you sure you want to remove this item ?";
AlertDialog.Builder builder = new AlertDialog.Builder(mContext, R.style.AlertDialogStyle);
builder.setTitle("Deleting..");;
builder.setPositiveButton("Remove", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
list.remove(holder.getAdapterPosition());
dataDb.removeItem(l.getId());
notifyDataSetChanged();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
AlertDialog alert = builder.create();
alert.getWindow().setLayout(600, 400);
alert.show();
}
});
}
@Override
public int getItemCount() {
return (list != null? list.size():0);
}
public class MyViewHolder extends RecyclerView.ViewHolder {
public TextView title;
public TextView caption;
ImageButton removeBtn;
public MyViewHolder(View itemView) {
super(itemView);
title = (TextView) itemView.findViewById(R.id.title);
caption = (TextView) itemView.findViewById(R.id.caption);
removeBtn = (ImageButton) itemView.findViewById(R.id.btnRemoveItem);
}
}
}
ActivityA.class
ActivityA.class
public class ActivityA extends Fragment {
List<ItemModel> list;
RecyclerView mRecyclerView;
RecyclerViewAdapter adapter;
ProgressBar progressBar;
DataDb dataDb;
EmptyRecyclerViewAdapter emptyRecyclerViewAdapter;
public ActivityA() {}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
View rootView = inflater.inflate(activity_one_layout, container, false);
progressBar = (ProgressBar) rootView.findViewById(R.id.progressBar);
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerview);
dataDb = new DataDb(getActivity());
list= dataDb .getList();
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
mRecyclerView.setLayoutManager(linearLayoutManager);
mRecyclerView.setHasFixedSize(true);
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
if(list == null || list.size() == 0) {
progressBar.setVisibility(View.GONE);
emptyRecyclerViewAdapter = new EmptyRecyclerViewAdapter("Empty Text Here!");
mRecyclerView.setAdapter(emptyRecyclerViewAdapter);
} else {
new LoadList().execute();
}
return rootView;
}
@Override
public void onResume() {
super.onResume();
}
private class LoadList extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
progressBar.setVisibility(View.VISIBLE);
}
@Override
protected Void doInBackground(Void... voids) {
try {
Thread.sleep(1000);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void params){
progressBar.setVisibility(View.GONE);
if(!list.isEmpty()) {
adapter = new RecyclerViewAdapter(getActivity(), list);
mRecyclerView.setAdapter(adapter);
adapter.notifyDataSetChanged();
} else {
Toast.makeText(getActivity(), "", Toast.LENGTH_SHORT).show();
}
}
}
}
图片1-输出结果
图片2-输出目标
推荐答案
您必须让您的Activity知道适配器中设置的列表已更改，并且项目计数降至零.当列表大小为空时，则需要从活动"中切换适配器.
You've to let your Activity know that the list set in adapter has changed and item count comes down to zero. When the list size gets empty then you'll need to switch the adapter from Activity.
您可以使用界面来实现.基本上，首先声明一个接口，并将其实例保存在Adapter中.每当您调用notifyDataSetChanged时，也应该调用此接口实例.这将触发在Activity中实现的Interface方法.您可以从那一点切换适配器.
You can achieve this with an Interface. Basically, declare an interface first and hold an instance of it in Adapter. Whenever you call notifyDataSetChanged, you should call this instance of Interface as well. This will trigger the Interface method implemented in Activity. You can switch the Adapter from that point.
像下面那样修改您的课程.
Modify your classes like following.
RecyclerViewAdapter.class
RecyclerViewAdapter.class
public class RecyclerViewAdapter extends RecyclerView.Adapter <RecyclerView.ViewHolder> {
//Declare an Interface which will work as a listener of notifyDataSetChanged.
// We'll then switch the adapter of Activity accordingly
public interface OnNotifyDataSetChanged {
void OnNotifyDataSetChangedFired(int dataSize);
}
private OnNotifyDataSetChanged onNotifyDataSetChanged;
private List<ItemModel> list;
private Context mContext = null;
public RecyclerViewAdapter (Context context, List<ItemModel> itemList, OnNotifyDataSetChanged onNotifyDataSetChanged) {
mContext = context;
this.list = itemList;
this.onNotifyDataSetChanged = onNotifyDataSetChanged;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
return new MyViewHolder(view);
}
@Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, int position) {
final ItemModel l = list.get(holder.getAdapterPosition());
final DataDb dataDb = new DataDb (mContext);
((MyViewHolder) holder).title.setText(l.getTitle());
((MyViewHolder) holder).caption.setText(l.getCaption());
((MyViewHolder) holder).removeBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String confirmText = "Are you sure you want to remove this item ?";
AlertDialog.Builder builder = new AlertDialog.Builder(mContext, R.style.AlertDialogStyle);
builder.setTitle("Deleting..");;
builder.setPositiveButton("Remove", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
list.remove(holder.getAdapterPosition());
dataDb.removeItem(l.getId());
notifyDataSetChanged();
// Trigger our Interface instance to let the Activity know that the adapter is updated
if(onNotifyDataSetChanged != null){
onNotifyDataSetChanged.OnNotifyDataSetChangedFired(list.size());
}
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
AlertDialog alert = builder.create();
alert.getWindow().setLayout(600, 400);
alert.show();
}
});
}
@Override
public int getItemCount() {
return (list != null? list.size():0);
}
public class MyViewHolder extends RecyclerView.ViewHolder {
public TextView title;
public TextView caption;
ImageButton removeBtn;
public MyViewHolder(View itemView) {
super(itemView);
title = (TextView) itemView.findViewById(R.id.title);
caption = (TextView) itemView.findViewById(R.id.caption);
removeBtn = (ImageButton) itemView.findViewById(R.id.btnRemoveItem);
}
}
}
ActivityA.class
ActivityA.class
public class ActivityA extends Fragment implements OnNotifyDataSetChanged {
List<ItemModel> list;
RecyclerView mRecyclerView;
RecyclerViewAdapter adapter;
ProgressBar progressBar;
DataDb dataDb;
EmptyRecyclerViewAdapter emptyRecyclerViewAdapter;
public ActivityA() {}
@Override
void OnNotifyDataSetChangedFired(int dataSize){
//Now, switch the adapter if needed
if(dataSize <= 0){
mRecyclerView.setAdapter(new EmptyRecyclerViewAdapter("Empty Text Here!"));
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
View rootView = inflater.inflate(activity_one_layout, container, false);
progressBar = (ProgressBar) rootView.findViewById(R.id.progressBar);
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerview);
dataDb = new DataDb(getActivity());
list= dataDb .getList();
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
mRecyclerView.setLayoutManager(linearLayoutManager);
mRecyclerView.setHasFixedSize(true);
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
if(list == null || list.size() == 0) {
progressBar.setVisibility(View.GONE);
emptyRecyclerViewAdapter = new EmptyRecyclerViewAdapter("Empty Text Here!");
mRecyclerView.setAdapter(emptyRecyclerViewAdapter);
} else {
new LoadList().execute();
}
return rootView;
}
@Override
public void onResume() {
super.onResume();
}
private class LoadList extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
progressBar.setVisibility(View.VISIBLE);
}
@Override
protected Void doInBackground(Void... voids) {
try {
Thread.sleep(1000);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void params){
progressBar.setVisibility(View.GONE);
if(!list.isEmpty()) {
// New updated constructor of the Adapter
adapter = new RecyclerViewAdapter(getActivity(), list, ActivityA.this);
mRecyclerView.setAdapter(adapter);
adapter.notifyDataSetChanged();
} else {
Toast.makeText(getActivity(), "", Toast.LENGTH_SHORT).show();
}
}
}
}
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