notifyDataSetChange() not updating DataGrid() via ArrayAdapter()

2023-03-30 06:46 问答作者：

In the code below have a variable of type List '<'String'>' named 'stringList' which is bound to a GridView view via and ArrayAdapter. The code below runs a for loop which creates a string and adds it to 'stringList'. As can be seen in the LogCat output the ArrayAdapter's getView() function is triggered when the OnCreate() sub routine concludes and the GridView is populated. What I want is for the GridView to populate one item at a time as each iteration of the for loop is run.

My research indicated that notifyDataSetObersver() function is the correct tool for accomplishing this. Although notifyDataSetObersver() is triggering in each iteration of the for loop it is not clear that it's doing anything, and my GridView is still getting populated after the onCreate() sub routine concludes.

If anyone has any suggestions I would be very appreciative.

*Please not the code below (as indicated in comments) relies on a the two layout resources titled "main" and "data_grid" pasted below the code.

Code:

package com.arrayadapterupdate2;

import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.text.Layout;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.GridView;
import android.widget.LinearLayout;
import android.widget.TextView;

public class Main extends Activity {

    LinearLayout mainLinearLayout;
    LayoutInflater inflater;
    GridArrayAdapter gridAdapter;
    GridView gridView;
    List<String> stringList;

    @Override
    public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);
        stringList = new ArrayList<String>();
        inflater = LayoutInflater.from(this);
        //The Resource 'mainLinearLayout' is a Linear Layout in the set content view 'main'
        mainLinearLayout = (LinearLayout) this.findViewById(R.id.mainLinearLayout);
        //The Resource 'grid_view' is a layout containing an empty gridview
        gridView = (GridView) inflater.inflate(R.layout.grid_view,null);
        gridAdapter = new GridArrayAdapter(this, stringList, R.layout.grid_view);
        gridView.setAdapter(gridAdapter);
        System.out.println("main triggered");
        stringList.clear();
        int i;
        int j =10;
            for (i=0;i<=j-1;i=i+1){
            System.out.println("Loop: "+i);
            String string;
            String addedString = "String "+i;
            stringList.add(addedString); 
            gridAdapter.notifyDataSetChanged();
            }
         mainLinearLayout.addView(gridView);
    }


public class GridArrayAdapter extends ArrayAdapter implements OnClickListener {

    private Context context;
    private List<String> stringList;

    public GridArrayAdapter(Context context, List<String> stringList, int id) {
        super(context, id, stringList);
        this.context = context;
        this.stringList = stringList;

    }   
@Override

    public View getView(int position, View convertView, ViewGroup viewGroup) {
         System.out.println("Get View Triggered "+ position);
         String string = stringList.get(position);
         LinearLayout gridViewElement = new LinearLayout(context);
         TextView textView = new TextView(context);
         textView.setText(string);
         gridViewElement.addView(textView);
        if (convertView == null) { 
            convertView = (View)gridViewElement;
        }  
        return convertView;
    }

@Override 

public void notifyDataSetChanged(){

System.out.println("Notify Data Set Changed Triggered");
}

@Override 

public int getCount() {

    return stringList.size();
}

@Override 

public Object getItem(int position) {

    return stringList.get(position);
}

@Override 

public long getItemId(int position) {

    return position;
}

@Override

public void onClick(View arg0) {

}
}

}

Portion of LogCat Output:

08-24 20:10:09.395: INFO/System.out(223): main triggered

08-24 20:10:09.395: INFO/System.out(223): Loop: 0

08-24 20:10:09.395: INFO/System.out(223): Notify Data Set Changed Triggered

08-24 20:10:09.395: INFO/System.out(223): Loop: 1

08-24 20:10:09.395: INFO/System.out(223): Notify Data Set Changed Triggered

08-24 20:10:09.395: INFO/System.out(223): Loop: 2

08-24 20:10:09.395: INFO/System.out(223): Notify Data Set Changed Triggered

08-24 20:10:09.395: INFO/System.out(223): Loop: 3