什麼是notifyItemRangeChanged（0，this.data.size（））;在這個例子中，它是如何工作的？

Question

我明白ViewHolder的onBindViewHolder是如何工作的，但我不清楚notifyItemRangeChanged(0, this.data.size());在這個例子中是如何工作的以及它究竟做了什麼。

提供給此適配器的數據爲Json格式。

適配器下面是：

public class AdapterQuestion extends RecyclerView.Adapter<AdapterQuestion.ViewQuestion>{ 

    private LayoutInflater mLayoutInflater; 

    //this is an arrayList of questionData objects 
    private ArrayList<QuestionData> data =new ArrayList<>(); 

    //Created the layoutInflator 
    public AdapterQuestion(Context context){ 
      //get from context 
      mLayoutInflater=LayoutInflater.from(context); 
    } 

    public void setBloglist(ArrayList<QuestionData> data){ 
     this.data =data; 
     notifyItemRangeChanged(0, this.data.size()); 
    } 

    @Override 
    public ViewQuestion onCreateViewHolder(ViewGroup parent, int viewType) { 
     //inflates the customQuestion view or converts it to java code 
     View view= mLayoutInflater.inflate(R.layout.customquestion, null); 

     //We now want to convert the View into a ViewQuestion, view Question takes 
     //a view so we pass the view into view question and then return it. 

     ViewQuestion holder=new ViewQuestion(view); 
     return holder; 
    } 

    //ViewGroup parent and ViewType are not being assigned. 
    @Override 
    public void onBindViewHolder(ViewQuestion holder, int position) { 
     //here we need to bind the data to our view, there is currently no Data! 
     //We need to get the data from our JSON 
     //Parameters is a ViewHolder and a Position 
     //This gives us the current information object from the whole arraylist 
     //data.get(position) data is the arraylist and we are getting the current position or index; 
     //That current obj is of Type QuestionData 

     QuestionData currentObj= data.get(position); 

     //we are accessing the Inflated view, or saved view with holder 
     //holder.answerText is the textView in holder. We are then taking that current object 
     //We are getting the text of the current object and setting it to the AnswerText view 
     holder.answerText.setText(currentObj.getMtext()); 
     holder.answerId.setText(currentObj.getId()); 
     holder.mVotes.setText(currentObj.getVotes()); 
     holder.mLikeButton.setTag(currentObj); 
    } 

    @Override 
    public int getItemCount() { 
     return data.size(); 
    } 

    public class ViewQuestion extends RecyclerView.ViewHolder{ 
     //once we create it once the reclycer view will automatically recycle it 
     private TextView answerText; 
     private TextView answerId; 
     private TextView mVotes; 
     private LikeButton mLikeButton; 

     public ViewQuestion (View itemView){ 
      super(itemView); 
      //here we are finding the views by their ID 
      answerText=(TextView)itemView.findViewById(R.id.answerText); 
      answerId=(TextView)itemView.findViewById(R.id.answerId); 
      mVotes=(TextView)itemView.findViewById(R.id.VoteTextView); 
      mLikeButton= (LikeButton)itemView.findViewById(R.id.heart_buttons); 

      mLikeButton.setOnLikeListener(new OnLikeListener() { 

       @Override 
       public void liked(LikeButton likeButton) { 
        Voting vote = new Voting(); 
        vote.onUpVote(convertToString(), 
          getAdapterPosition(),ViewQuestion.this); 
        System.out.print("Adapter Position"+getAdapterPosition()); 
       } 

       @Override 
       public void unLiked(LikeButton likeButton) { 
        Voting onDown=new Voting(); 
        onDown.onDownVote(convertToString(), 
          getAdapterPosition(), ViewQuestion.this); 

       } 
      }); 
     } 

     public String getVoteView(){ 
      String voteView=mVotes.getText().toString(); 
      return voteView; 
     } 

     public String convertToString(){ 
      String converted=answerId.getText().toString(); 
      return converted; 
     } 

     public int convertToInt(){ 
      String converted=answerId.getText().toString(); 
      int ConvertedInt=Integer.parseInt(converted); 
      return ConvertedInt; 
     } 
    } 
} 

Answer 1

當這是在RecyclerView要設置的數據發生變化時，適配器需要得到通知的數據變化，以便它可以更改數據在recyclerview。

的方法

notifyItemRangedChanged(fromIndex,toIndex); 

被用於通知一些數據集是整個數據中改變適配器，它告訴該適配器應該刷新數據，並重新將其recyclerView從啓動適配器從傳入到方法的fromIndex到toIndex。

如果您有多個數據已更改但不是全部，那些已更改的數據也位於羣集中，因此您可以說從5日到10日索引數據發生更改。

如果所有的數據被更改電話：

notifyDataSetChanged(); 

如果只有一個DataItem的改變，然後調用：

notifyItemChanged(dataPosition); 

Answer 2

你的情況

你不這樣做（notifyItemRangeChanged）權利，你還不如那麼可以調用notifyDataSetChanged();，因爲您告訴適配器整個列表已經更改，而不是特定的位置。

Answer 3

使用notifyItemRangeChanged（0，this.data.size（））這是不好的做法。 最好的方法是使用notifyItemChanged或notifyItemRangeChanged與有效載荷。

有效負載 - 可選參數（鍵）。這給你機會來檢查你需要什麼樣的更新。

public void onBindViewHolder(/*...*/, List payloads) { 
    if (payloads.isEmpty()) { 
     setText(holder, position); 
     downloadBitmap(holder, position); 
    } else if (payloads.contains(SET_ONLY_TEXT)){ 
     setText(holder, position); 
    } 
} 

在本示例中，有效負載用於檢查適配器何時應僅更新文本。