List MediaStore.Images.Thumbnails in GridView, with custom SimpleCursorAdapter.

Last exercise list MediaStore.Images.Thumbnails in ListView, with custom SimpleCursorAdapter. It's easy to be modified to display in GridView.

Modify /res/layout/row.xml to have a ImageView only in each grid.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">
    
    <ImageView
        android:id="@+id/thumb"
        android:layout_width="100dp"
        android:layout_height="100dp"/>

</LinearLayout>

Modify layout to have a GridView.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" 
    android:orientation="vertical">

    <GridView
        android:id="@+id/gridview"
        android:layout_width="fill_parent" 
        android:layout_height="fill_parent"
        android:columnWidth="100dp"
        android:numColumns="auto_fit"
        android:verticalSpacing="10dp"
        android:horizontalSpacing="10dp"
        android:stretchMode="columnWidth"
        android:gravity="center"/>

</LinearLayout>

Modify the code extends Activity with GridView, instead of ListActivity.

package com.example.androidlistimages;

import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.v4.content.CursorLoader;
import android.support.v4.widget.CursorAdapter;
import android.support.v4.widget.SimpleCursorAdapter;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.Toast;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

public class MainActivity extends Activity {
 
 //define source of MediaStore.Images.Media, internal or external storage
 final Uri sourceUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
 final Uri thumbUri = MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI;
 final String thumb_DATA = MediaStore.Images.Thumbnails.DATA;
 final String thumb_IMAGE_ID = MediaStore.Images.Thumbnails.IMAGE_ID;

 //SimpleCursorAdapter mySimpleCursorAdapter;
 MyAdapter mySimpleCursorAdapter;
 
 GridView myGridView;
 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        myGridView = (GridView)findViewById(R.id.gridview);
        
        String[] from = {MediaStore.MediaColumns.TITLE};
        int[] to = {android.R.id.text1};

        CursorLoader cursorLoader = new CursorLoader(
          this, 
          sourceUri, 
          null, 
          null, 
          null, 
          MediaStore.Audio.Media.TITLE);
        
        Cursor cursor = cursorLoader.loadInBackground();
        
        mySimpleCursorAdapter = new MyAdapter(
          this, 
          android.R.layout.simple_list_item_1, 
          cursor, 
          from, 
          to, 
          CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);
        
        myGridView.setAdapter(mySimpleCursorAdapter);
        myGridView.setOnItemClickListener(myOnItemClickListener);
    }
    
    OnItemClickListener myOnItemClickListener
    = new OnItemClickListener(){

  @Override
  public void onItemClick(AdapterView<?> parent, View view, int position,
    long id) {
   Cursor cursor = mySimpleCursorAdapter.getCursor();
   cursor.moveToPosition(position);

   int int_ID = cursor.getInt(cursor.getColumnIndex(MediaStore.Images.Media._ID));
   getThumbnail(int_ID);
  }};
 
 private Bitmap getThumbnail(int id){

  String[] thumbColumns = {thumb_DATA, thumb_IMAGE_ID};

  CursorLoader thumbCursorLoader = new CursorLoader(
          this, 
          thumbUri, 
    thumbColumns, 
    thumb_IMAGE_ID + "=" + id, 
    null, 
    null);
        
        Cursor thumbCursor = thumbCursorLoader.loadInBackground();
        
        Bitmap thumbBitmap = null;
        if(thumbCursor.moveToFirst()){
   int thCulumnIndex = thumbCursor.getColumnIndex(thumb_DATA);
   
   String thumbPath = thumbCursor.getString(thCulumnIndex);
   
   Toast.makeText(getApplicationContext(), 
     thumbPath, 
     Toast.LENGTH_LONG).show();
   
   thumbBitmap = BitmapFactory.decodeFile(thumbPath);
   
   //Create a Dialog to display the thumbnail
   AlertDialog.Builder thumbDialog = new AlertDialog.Builder(MainActivity.this);
   ImageView thumbView = new ImageView(MainActivity.this);
   thumbView.setImageBitmap(thumbBitmap);
   LinearLayout layout = new LinearLayout(MainActivity.this);
         layout.setOrientation(LinearLayout.VERTICAL);
         layout.addView(thumbView);
         thumbDialog.setView(layout);
         thumbDialog.show();
   
  }else{
   Toast.makeText(getApplicationContext(), 
     "NO Thumbnail!", 
     Toast.LENGTH_LONG).show();
  }
        
        return thumbBitmap;
 }
 
 public class MyAdapter extends SimpleCursorAdapter{
  
  Cursor myCursor;
     Context myContext;

  public MyAdapter(Context context, int layout, Cursor c, String[] from,
    int[] to, int flags) {
   super(context, layout, c, from, to, flags);
   
   myCursor = c;
      myContext = context;
  }

  @Override
  public View getView(int position, View convertView, ViewGroup parent) {
   View row = convertView;
   if(row==null){
    LayoutInflater inflater=getLayoutInflater();
    row=inflater.inflate(R.layout.row, parent, false); 
   }
   
   ImageView thumbV = (ImageView)row.findViewById(R.id.thumb);
   
   myCursor.moveToPosition(position);
   
   int myID = myCursor.getInt(myCursor.getColumnIndex(MediaStore.Images.Media._ID));
   
   String[] thumbColumns = {thumb_DATA, thumb_IMAGE_ID};
   CursorLoader thumbCursorLoader = new CursorLoader(
     myContext, 
           thumbUri, 
     thumbColumns, 
     thumb_IMAGE_ID + "=" + myID, 
     null, 
     null);
   Cursor thumbCursor = thumbCursorLoader.loadInBackground();
   
   Bitmap myBitmap = null;
         if(thumbCursor.moveToFirst()){
    int thCulumnIndex = thumbCursor.getColumnIndex(thumb_DATA);
    String thumbPath = thumbCursor.getString(thCulumnIndex);
    myBitmap = BitmapFactory.decodeFile(thumbPath);
    thumbV.setImageBitmap(myBitmap);
   }
   
   return row;
  }
  
 }
}

Download the files.