放置在哪里notifyDataSetChanged（）;在customAdapter所以listView不会丢失滚动数据

Question

我知道有关于notifyDataSetChanged（）的在线信息;以及如何使用它，但我似乎无法弄清楚如何将其用于我的确切情况。我不知道我是否应该在我的活动，适配器类或什么中调用它。我只是希望listView不会更改用户以前输入的文本，以便在行从屏幕滚动时返回到默认文本。

MainActivity.java

import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.app.Activity; 
import android.view.KeyEvent; 
import android.view.View; 
import android.view.inputmethod.EditorInfo; 
import android.widget.AdapterView; 
import android.widget.ArrayAdapter; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.ListAdapter; 
import android.widget.ListView; 
import android.widget.TextView; 
import android.widget.Toast; 
import android.widget.ViewSwitcher; 

import java.util.ArrayList; 

public class MainActivity extends Activity { 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     final ArrayList<String> Chores = new ArrayList<>(); 
     Chores.add(""); 

     final ListAdapter MyAdapter = new CustomAdapter(this, Chores); 
     ListView listViewObject = (ListView)findViewById(R.id.customListView_ID); 
     listViewObject.setAdapter(MyAdapter); 

     listViewObject.setOnItemClickListener(
      new AdapterView.OnItemClickListener(){ 
       @Override 
       public void onItemClick(AdapterView<?> parent, View view, int position, long id){ 
        String ChoreString = String.valueOf(parent.getItemAtPosition(position)); 




       } 
      } 

     ); 
     final Button button = (Button) findViewById(R.id.button_ID); 
     button.setOnClickListener(new View.OnClickListener() { 
      public void onClick(View v) { 
       Chores.add(""); 
       ((ArrayAdapter)MyAdapter).notifyDataSetChanged(); 

      } 

     }); 




    } 
} 

CustomAdapter.java

import android.content.Context; 
import android.content.DialogInterface; 
import android.support.annotation.NonNull; 
import android.support.v7.app.AlertDialog; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ArrayAdapter; 
import android.widget.EditText; 
import android.widget.ImageButton; 
import android.widget.ImageView; 
import android.widget.TextView; 

import java.util.ArrayList; 

import static com.example.emilythacker.chorelist.R.id.textView_ID; 



class CustomAdapter extends ArrayAdapter{ 

    public CustomAdapter(Context context, ArrayList choreText) { 
     super(context, R.layout.custon_listview_row, choreText); 
    } 

    @NonNull 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     LayoutInflater myInflater = LayoutInflater.from(getContext()); 
     View customView = myInflater.inflate(R.layout.custon_listview_row, parent, false); 


     ImageButton imageButton = (ImageButton) customView.findViewById(R.id.imageButton_ID); 
     final TextView textView = (TextView) customView.findViewById(textView_ID); 





     textView.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       //what happens when textView is clicked 
       AlertDialog alertDialog = new AlertDialog.Builder(getContext()).create(); 
       final EditText input = new EditText(getContext()); 
       input.setHint("hint"); 
       alertDialog.setView(input); 
       alertDialog.setTitle("Set Chore"); 
       alertDialog.setMessage("Alert message to be shown"); 
       alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK", new DialogInterface.OnClickListener() { 
          public void onClick(DialogInterface dialog, int which) { 

           //this will set text to "hello" only if user does not enter anything into input 
           //textView.setText("hello"); 

           //this also will only work if there is no input entered into input...wich will change textView into empty space 
           textView.setText(input.getText().toString()); 




           //works the same with or without dialog.dismiss(); 
           dialog.dismiss(); 
          } 
         }); 
       alertDialog.show(); 

      } 
     }); 



     imageButton.setImageResource(R.drawable.clock); 


     return customView; 
    } 
} 

Answer 1

的问题不是由notifyDataSetChanged引起（）;但是因为您没有在您的适配器中重复使用您的视图，也没有在您的getView中设置要设置的数据，所以最好尝试使用视图模式或使用recyclerview。

class CustomAdapter extends ArrayAdapter{ 

    ArrayList<String> choreText; 

    public CustomAdapter(Context context, ArrayList choreText) { 
     super(context, R.layout.custon_listview_row, choreText); 
     this.choreText = choreText; 
    } 

    @NonNull 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     ViewHolder holder; 
     if (convertView == null) { 
      LayoutInflater layoutInflater = LayoutInflater.from(getContext()); 
      convertView = layoutInflater.inflate(R.layout.custon_listview_row, parent, false); 
      holder = new ViewHolder(); 
      holder.imageButton = (ImageButton) customView.findViewById(R.id.imageButton_ID); 
      holder.textView = (TextView) customView.findViewById(textView_ID); 
      convertView.setTag(holder); 
     } else { 
      holder = (ViewHolder) convertView.getTag(); 
     } 

     holder.textView.setText(choreText.get(position)); 
     holder.textView.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       //what happens when textView is clicked 
       AlertDialog alertDialog = new AlertDialog.Builder(getContext()).create(); 
       final EditText input = new EditText(getContext()); 
       input.setHint("hint"); 
       alertDialog.setView(input); 
       alertDialog.setTitle("Set Chore"); 
       alertDialog.setMessage("Alert message to be shown"); 
       alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK", new DialogInterface.OnClickListener() { 
          public void onClick(DialogInterface dialog, int which) { 

           //this will set text to "hello" only if user does not enter anything into input 
           //textView.setText("hello"); 

           //this also will only work if there is no input entered into input...wich will change textView into empty space 
           textView.setText(input.getText().toString()); 




           //works the same with or without dialog.dismiss(); 
           dialog.dismiss(); 
          } 
         }); 
       alertDialog.show(); 

      } 
     }); 



     holder.imageButton.setImageResource(R.drawable.clock); 


     return customView; 
    } 

    static class ViewHolder { 
     ImageButton imageButton; 
     TextView textView; 
    } 
} 

Answer 2

1. 不要从您的MainActivity加空字符串到list.Remove所有Chores.add("");。

2.滚动它将重新创建视图更好的选项来使用视图持有人虽然。

3.要保存视图数据，请创建一个存储edittext文本数据的数组。

// initialise the array inside constructor 
    stringArray = new String[choreText.size()] ; 

4.On每OK点击数据保存到阵列，并呼吁notifyDataSetChanged

alertDialog.setButton(AlertDialog.BUTTON_NE UTRAL, "OK", new DialogInterface.OnClickListener() 
    { public void onClick(DialogInterface dialog, int which) { 

    //this will set text to "hello" only if user does not enter anything into input 
    textView.setText("hello"); 

    //this also will only work if there is no input entered into input...which will change textView into empty space 

    textView.setText(input.getText().toString()); 
    stringArray[position]=input.getText().toString(); 
    notifyDataSetChanged(); 

    //works the same with or without 
    dialog.dismiss(); dialog.dismiss(); } }); 

4.设置从数组中保存的文本，里面你getview加入这一行

textview.setText(stringArray[position]==null?"":stringArray[position];