Android-GridView

package com.cs.dxm.gridviewtest;

import android.content.Context;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.*;
import android.widget.*;

public class MainActivity extends AppCompatActivity {
    Integer[] imageIDs = {
            R.drawable.pic1,
            R.drawable.pic2,
            R.drawable.pic3,
            R.drawable.pic4,
            R.drawable.pic5,
            R.drawable.pic6,
            R.drawable.pic7
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
        GridView gridView = (GridView) findViewById(R.id.gridview);
        gridView.setAdapter(new ImageAdapter(this));

        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener()
        {
            public void onItemClick(AdapterView parent,
                                    View v, int position, long id)
            {
                Toast.makeText(getBaseContext(),
                        "pic" + (position + 1) + " selected",
                        Toast.LENGTH_SHORT).show();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public class ImageAdapter extends BaseAdapter
    {
        private Context context;

        public ImageAdapter(Context c)
        {
            context = c;
        }

        //---returns the number of images---
        public int getCount() {
            return imageIDs.length;
        }

        //---returns the item---
        public Object getItem(int position) {
            return position;
        }

        //---returns the ID of an item---
        public long getItemId(int position) {
            return position;
        }

        //---returns an ImageView view---
        public View getView(int position, View convertView,
                            ViewGroup parent)
        {
            ImageView imageView;
            if (convertView == null) {
                imageView = new ImageView(context);
                imageView.setLayoutParams(new
                        GridView.LayoutParams(170, 170));
                imageView.setScaleType(
                        ImageView.ScaleType.CENTER_CROP);
                imageView.setPadding(5, 5, 5, 5);
            } else {
                imageView = (ImageView) convertView;
            }
            imageView.setImageResource(imageIDs[position]);
            return imageView;
        }
    }
}

/*******************************************************************/

    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    android:id="@+id/gridview"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    android:numColumns="auto_fit"
    android:verticalSpacing="10dp"
    android:horizontalSpacing="10dp"
    android:columnWidth="90dp"
    android:stretchMode="columnWidth"
    android:gravity="center" />