LanguageActivity.java

package com.example.gitnb.module;

import android.content.Intent;
import android.graphics.Rect;
import android.os.Bundle;
import android.os.Build.VERSION;
import android.os.Build.VERSION_CODES;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.MotionEvent;
import android.view.View;

import com.example.gitnb.R;
import com.example.gitnb.utils.Utils;

public class LanguageActivity  extends AppCompatActivity {
    public static String LANGUAGE_KEY = "language_key";
    private RecyclerView recyclerView;
    private LanguageAdapter adapter;
    private static int COLUM_NUM = 4;
    private static int ITEM_SPACE = 20;
    private int item_space;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if(VERSION.SDK_INT >= VERSION_CODES.LOLLIPOP) {
        	getWindow().setStatusBarColor(getResources().getColor((R.color.transparent_dark_gray)));
        }
        setContentView(R.layout.activity_language);
        item_space = Utils.dpToPx(this, ITEM_SPACE);
        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        adapter = new LanguageAdapter(this);
        adapter.SetOnItemClickListener(new LanguageAdapter.OnItemClickListener() {
			
			@Override
			public void onItemClick(View view, int position) {
				Intent intent=new Intent();
			    intent.putExtra(LANGUAGE_KEY, adapter.getItemValue(position));
			    setResult(RESULT_OK, intent);
			    finish();
			}
		});
        recyclerView.setAdapter(adapter);
        recyclerView.addItemDecoration(new GridSpacingItemDecoration(COLUM_NUM, item_space, true));
        recyclerView.setLayoutManager(new GridLayoutManager(this, COLUM_NUM));
        //recyclerView.setItemAnimator(new DefaultItemAnimator());
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
	    setResult(RESULT_CANCELED, null);
        finish();
        return true;
    }
    
    public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

        private int spanCount;
        private int spacing;
        private boolean includeEdge;

        public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {
            this.spanCount = spanCount;
            this.spacing = spacing;
            this.includeEdge = includeEdge;
        }

        @Override
        public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
            int position = parent.getChildAdapterPosition(view); // item position
            int column = position % spanCount; // item column

            if (includeEdge) {
                outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
                outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)
//                if (position < spanCount) { // top edge
//                    outRect.top = spacing;
//                }
//                outRect.bottom = spacing; // item bottom
                if (position >= spanCount) {
                    outRect.top = spacing; // item top
                }
            } else {
                outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
                outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
                if (position >= spanCount) {
                    outRect.top = spacing; // item top
                }
            }
        }
    }
}