GridView sorunu

package com.example.wallpapergirisim;

import android.app.WallpaperManager;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridLayout;
import android.widget.GridView;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    Integer[] myImageArray={
            R.drawable.thumb1,R.drawable.thumb2,
            R.drawable.thumb3,R.drawable.thumb4

    };
    GridView myg;
    ImageView myCurrentWallpaper;
    WallpaperManager myWallManager;
    Drawable myDrawable;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

       myg=findViewById(R.id.myg);
        myCurrentWallpaper=findViewById(R.id.myCurrentWallpaper);

        myg.setAdapter(new ImageAdapter(getApplicationContext()));
        //UpdateMyWallpaper();

    }

    private void UpdateMyWallpaper(){

       // myWallManager=WallpaperManager.getInstance(getApplicationContext());
        //myDrawable=myWallManager.getDrawable();
       // myCurrentWallpaper.setImageDrawable(myDrawable);
    }

    public class ImageAdapter extends BaseAdapter{

        Context myContex;

        public ImageAdapter(Context applicationContext) {
            myContex=applicationContext;
        }

        @Override
        public int getCount() {
            return myImageArray.length;
        }

        @Override
        public Object getItem(int position) {
            return null;
        }

        @Override
        public long getItemId(int position) {
            return 0;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            ImageView GridImageView;

            if(convertView == null){
                GridImageView=new ImageView(myContex);
                GridImageView.setLayoutParams(new GridView.LayoutParams(512,512));
                GridImageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            }else{

                GridImageView=(ImageView) convertView;
            }

            GridImageView.setImageResource(myImageArray[position]);
            return GridImageView;
        }
    }


}

Android için bir wallpaper uygulaması geliştiremeye çalıştırıoyrum kodlarım bunlar.Fakat programı hem emülatör hemde telefon da çalıştırdığımda uygulama ne yazıkki durdu diyor.Yardımcı olurmusunuz acaba nerde hatam var?