[英]Android Firebase Recyclerview Adapter is not populating with data - mSnapshots is 0
[英]Where to manipulate the data in Recyclerview Adapter (Android)
我的日期時間當前存儲為UNIX時間戳。 我想在Recyclerview中將其顯示為h:mm a。
我應該在哪里將UNIX時間戳轉換為RecyclerView Adapter / Viewholder中的正常時間(就最佳性能而言)?
我應該在RecyclerView.Adapter
的getItemViewType(int position)
還是onBindViewHolder
或ViewHolder
類的bind
函數中執行此ViewHolder
?
編輯:我的代碼
public class ChatListAdapter extends RecyclerView.Adapter {
private final LayoutInflater mInflater;
private List<Chat> mChats;
private final String ownerMe = "OWNER_ME";
private static final int VIEW_TYPE_MESSAGE_ME = 1;
private static final int VIEW_TYPE_MESSAGE_ME_CORNER = 2;
private static final int VIEW_TYPE_MESSAGE_BF = 3;
private static final int VIEW_TYPE_MESSAGE_BF_CORNER = 4;
ChatListAdapter(Context context) {mInflater = LayoutInflater.from(context);}
@Override
public int getItemViewType(int position) {
Chat chat = mChats.get(position);
if(chat.getUser().equals(ownerMe)) {
if(position == mChats.size()-1) {
return VIEW_TYPE_MESSAGE_ME_CORNER;
}
if(chat.getUser().equals(mChats.get(position+1).getUser())) {
return VIEW_TYPE_MESSAGE_ME;
} else {
return VIEW_TYPE_MESSAGE_ME_CORNER;
}
} else {
if(position == mChats.size()-1) {
return VIEW_TYPE_MESSAGE_BF_CORNER;
}
if(chat.getUser().equals(mChats.get(position+1).getUser())) {
return VIEW_TYPE_MESSAGE_BF;
} else {
return VIEW_TYPE_MESSAGE_BF_CORNER;
}
}
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view;
if(viewType == VIEW_TYPE_MESSAGE_ME || viewType == VIEW_TYPE_MESSAGE_ME_CORNER) {
view = mInflater.inflate(R.layout.recyclerview_item_right, parent, false);
return new MeMessageHolder(view);
} else if (viewType == VIEW_TYPE_MESSAGE_BF || viewType == VIEW_TYPE_MESSAGE_BF_CORNER) {
view = mInflater.inflate(R.layout.recyclerview_item_left, parent, false);
return new BfMessageHolder(view);
}
return null;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
if (mChats != null) {
Chat current = mChats.get(position);
long unixTime= current.getUnixTime();
Date time = new java.util.Date(unixTime*1000L);
SimpleDateFormat sdf = new java.text.SimpleDateFormat("h:mm a");
String formattedTime = sdf.format(time);
switch (holder.getItemViewType()) {
case VIEW_TYPE_MESSAGE_ME:
((MeMessageHolder) holder).bind(current, formattedTime, false);
break;
case VIEW_TYPE_MESSAGE_ME_CORNER:
((MeMessageHolder) holder).bind(current, formattedTime, true);
break;
case VIEW_TYPE_MESSAGE_BF:
((BfMessageHolder) holder).bind(current, formattedTime, false);
break;
case VIEW_TYPE_MESSAGE_BF_CORNER:
((BfMessageHolder) holder).bind(current, formattedTime, true);
break;
}
}
}
class MeMessageHolder extends RecyclerView.ViewHolder {
private final TextView chatItemView;
private final ImageView cornerRightIImageView;
private final ConstraintLayout constraintLayout;
private final TextView timeItemView;
private MeMessageHolder(View itemView) {
super(itemView);
chatItemView = itemView.findViewById(R.id.textView);
cornerRightIImageView = itemView.findViewById(R.id.corner_view_right);
constraintLayout = itemView.findViewById(R.id.chat_bubble_id);
timeItemView = itemView.findViewById(R.id.text_message_time);
}
void bind(Chat chat, String formattedTime, boolean isCorner) {
chatItemView.setText(chat.getMessage());
timeItemView.setText(formattedTime);
if(isCorner) {
constraintLayout.setBackgroundResource(R.drawable.chat_bubble_v2);
} else {
cornerRightIImageView.setVisibility(View.INVISIBLE);
}
}
}
class BfMessageHolder extends RecyclerView.ViewHolder {
private final TextView chatItemView;
private final ImageView cornerLeftImageView;
private final ConstraintLayout constraintLayout;
private final TextView timeItemView;
private BfMessageHolder(View itemView) {
super(itemView);
chatItemView = itemView.findViewById(R.id.textView);
cornerLeftImageView = itemView.findViewById(R.id.corner_view_left);
constraintLayout = itemView.findViewById(R.id.chat_bubble_id);
timeItemView = itemView.findViewById(R.id.text_message_time);
}
void bind(Chat chat, String formattedTime, boolean isCorner) {
chatItemView.setText(chat.getMessage());
timeItemView.setText(formattedTime);
if(isCorner) {
constraintLayout.setBackgroundResource(R.drawable.chat_bubble_v3);
} else {
cornerLeftImageView.setVisibility(View.INVISIBLE);
}
}
}
void setChats(List<Chat> chats) {
mChats = chats;
notifyDataSetChanged();
}
@Override
public int getItemCount() {
if(mChats!=null)
return mChats.size();
else return 0;
}
}
這是方法正確嗎? 我在onBindViewHolder
方法中格式化了日期
這取決於您是要在recyclerview的不同項目上顯示不同的日期,還是要在recyclerview的所有項目上顯示相同的日期。 如果要對所有項目顯示相同的日期,最好在適配器之外進行,然后將解析的日期傳遞給recyclerview適配器。 或者,如果要在每個項目上顯示不同的日期,則應在onBindViewHolder中執行此操作,因為它可以訪問項目位置。
請記住,getItemViewType用於從可用視圖類型中獲取視圖類型。 如果要放大多個視圖,則使用此方法。 考慮一個chatapp,其中view1將在左側顯示消息,而view2將在右側顯示消息; 全部都在同一recyclerview中。
onBindViewHolder方法僅執行通用綁定任務。 綁定內容:展開視圖的項目和數據。
似乎是業務邏輯。 因此,例如,我建議您在Model中將UNIX時間戳轉換。
class Chat {
private Long unixTime;
// another code
public Long getUnixTime() {
return unixTime;
}
public String convertedUnixTimeToString(String format) {
// Also need to add some format validation
if(format == null) {
// do some action, like trowing exception, or setting default value in format
}
Date time = new java.util.Date(unixTime*1000L);
SimpleDateFormat sdf = new java.text.SimpleDateFormat(format);
return sdf.format(time);
}
}
我建議您使用JodaTime進行日期和時間格式設置。 非常有用的東西。
然后,只需修改您的代碼
public class ChatListAdapter extends RecyclerView.Adapter {
private final LayoutInflater mInflater;
private List<Chat> mChats;
private final String ownerMe = "OWNER_ME";
private static final int VIEW_TYPE_MESSAGE_ME = 1;
private static final int VIEW_TYPE_MESSAGE_ME_CORNER = 2;
private static final int VIEW_TYPE_MESSAGE_BF = 3;
private static final int VIEW_TYPE_MESSAGE_BF_CORNER = 4;
ChatListAdapter(Context context) {mInflater = LayoutInflater.from(context);}
@Override
public int getItemViewType(int position) {
Chat chat = mChats.get(position);
if(chat.getUser().equals(ownerMe)) {
if(position == mChats.size()-1) {
return VIEW_TYPE_MESSAGE_ME_CORNER;
}
if(chat.getUser().equals(mChats.get(position+1).getUser())) {
return VIEW_TYPE_MESSAGE_ME;
} else {
return VIEW_TYPE_MESSAGE_ME_CORNER;
}
} else {
if(position == mChats.size()-1) {
return VIEW_TYPE_MESSAGE_BF_CORNER;
}
if(chat.getUser().equals(mChats.get(position+1).getUser())) {
return VIEW_TYPE_MESSAGE_BF;
} else {
return VIEW_TYPE_MESSAGE_BF_CORNER;
}
}
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view;
if(viewType == VIEW_TYPE_MESSAGE_ME || viewType == VIEW_TYPE_MESSAGE_ME_CORNER) {
view = mInflater.inflate(R.layout.recyclerview_item_right, parent, false);
return new MeMessageHolder(view);
} else if (viewType == VIEW_TYPE_MESSAGE_BF || viewType == VIEW_TYPE_MESSAGE_BF_CORNER) {
view = mInflater.inflate(R.layout.recyclerview_item_left, parent, false);
return new BfMessageHolder(view);
}
return null;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
if (mChats != null) {
Chat current = mChats.get(position);
switch (holder.getItemViewType()) {
case VIEW_TYPE_MESSAGE_ME:
((MeMessageHolder) holder).bind(current, false);
break;
case VIEW_TYPE_MESSAGE_ME_CORNER:
((MeMessageHolder) holder).bind(current, true);
break;
case VIEW_TYPE_MESSAGE_BF:
((BfMessageHolder) holder).bind(current, false);
break;
case VIEW_TYPE_MESSAGE_BF_CORNER:
((BfMessageHolder) holder).bind(current, true);
break;
}
}
}
class MeMessageHolder extends RecyclerView.ViewHolder {
private final TextView chatItemView;
private final ImageView cornerRightIImageView;
private final ConstraintLayout constraintLayout;
private final TextView timeItemView;
private MeMessageHolder(View itemView) {
super(itemView);
chatItemView = itemView.findViewById(R.id.textView);
cornerRightIImageView = itemView.findViewById(R.id.corner_view_right);
constraintLayout = itemView.findViewById(R.id.chat_bubble_id);
timeItemView = itemView.findViewById(R.id.text_message_time);
}
void bind(Chat chat, boolean isCorner) {
chatItemView.setText(chat.getMessage());
timeItemView.setText(chat.convertedUnixTimeToString("h:mm a"));
if(isCorner) {
constraintLayout.setBackgroundResource(R.drawable.chat_bubble_v2);
} else {
cornerRightIImageView.setVisibility(View.INVISIBLE);
}
}
}
class BfMessageHolder extends RecyclerView.ViewHolder {
private final TextView chatItemView;
private final ImageView cornerLeftImageView;
private final ConstraintLayout constraintLayout;
private final TextView timeItemView;
private BfMessageHolder(View itemView) {
super(itemView);
chatItemView = itemView.findViewById(R.id.textView);
cornerLeftImageView = itemView.findViewById(R.id.corner_view_left);
constraintLayout = itemView.findViewById(R.id.chat_bubble_id);
timeItemView = itemView.findViewById(R.id.text_message_time);
}
void bind(Chat chat, boolean isCorner) {
chatItemView.setText(chat.getMessage());
timeItemView.setText(chat.convertedUnixTimeToString("h:mm a"));
if(isCorner) {
constraintLayout.setBackgroundResource(R.drawable.chat_bubble_v3);
} else {
cornerLeftImageView.setVisibility(View.INVISIBLE);
}
}
}
void setChats(List<Chat> chats) {
mChats = chats;
notifyDataSetChanged();
}
@Override
public int getItemCount() {
if(mChats!=null)
return mChats.size();
else return 0;
}
}
您需要通過將時間戳乘以1000來將其轉換為毫秒:
java.util.Date dateTime=new java.util.Date((long)timeStamp*1000);
然后首先您需要將UNIX時間戳轉換為日期時間格式
final long unixTime = 1372339860;
final String formattedDtm = Instant.ofEpochSecond(unixTime)
.atZone(ZoneId.of("GMT-4"))
.format(formatter);
System.out.println(formattedDtm); // => '2013-06-27 09:31:00'
那么您想將此數據存儲到RecyclerView的字段值,然后可以從這種時間格式像h:mm
格式化
您應該在onBindViewHolder
方法中更新UI更改。 您可以在onBindViewHolder
調用ViewHolder
bind
方法。
例:
public class SampleAdapter extends RecyclerView.Adapter<SampleAdapter.ViewHolder> {
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.sample_view, viewGroup, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull ViewHolder viewHolder, int i) {
viewHolder.bind(i);
}
public class ViewHolder extends RecyclerView.ViewHolder {
public ViewHolder(@NonNull View itemView) {
super(itemView);
}
void bind(int position) {
// Do your data updates here.
}
}
}
只需將SimpleDateFormat
與yyyy-MM-dd
模式一起使用即可。
在RecyclerView.
onBindViewHolder
方法中應用SimpleDateFormat.format(millis)
RecyclerView.
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