我知道在线上有关于notifyDataSetChanged（）的信息；以及如何使用它，但我似乎无法弄清楚如何针对我的实际情况使用它。我不知道该在我的活动，适配器类还是什么中调用它。我只希望listView不更改该行滚动到屏幕之外时用户先前输入的文本，以返回到默认文本。
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;
}
}
最佳答案
该问题不是由notifyDataSetChanged（）引起的；但是因为您没有在适配器中重用视图并且没有设置要在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;
}
}
关于android - 在哪里放置notifyDataSetChanged();在customAdapter中，这样listView不会在滚动时丢失数据，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/41353995/