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在我的确切情况下使用它。我不知道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不会更改用户先前输入的文本，以便在行滚动屏幕时返回默认文本。

MainActivity.java

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CustomAdapter.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();

            }

        });




    }
}

Answer 1

问题不是由notifyDataSetChanged（）引起的;但是因为您没有在适配器中重复使用视图而没有设置要在getView（）中设置的数据

最好尝试使用viewholder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

不要在列表中添加空字符串。从MainActivity中移除所有Chores.add("");。

2.在滚动时，它会重新创建视图，以便更好地使用视图持有者。

3.要保留视图数据，请创建一个用于存储edittext文本数据的数组。

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

4.每次点击都会点击将数据保存到数组中并调用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.从数组中设置保留的文本，在getview中添加此行

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

放置notifyDataSetChanged（）的位置;在customAdapter中，listView不会丢失滚动数据

2 个答案: