MainActivity.java

package com.nicksapp.testproject;

import android.Manifest;
import android.annotation.TargetApi;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    String PERM_GALERY = Manifest.permission.READ_EXTERNAL_STORAGE;
    List<String> paths;
    GridAdapter adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if(checkPermision()){
            paths = getImagePaths(this);
        }

    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if(ContextCompat.checkSelfPermission(this, PERM_GALERY) == PackageManager.PERMISSION_GRANTED){
            paths = getImagePaths(this);    //Требуется разрешение
            Log.d("LOG: ", "Done!");
        }else{
            requestPermissions(
                    new String[]{PERM_GALERY},
                    1);
        }
        super.onActivityResult(requestCode, resultCode, data);
    }
    @TargetApi(22)
    boolean checkPermision(){
        if(ContextCompat.checkSelfPermission(this, PERM_GALERY) == PackageManager.PERMISSION_GRANTED){
            return true;
        }else{
            ActivityCompat.requestPermissions(this,
                    new String[]{PERM_GALERY},
                    1);
            return false;
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch(requestCode){
            case 1:
                if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                    paths = getImagePaths(this);
                }
                break;
            default:
        }
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }

    public List<String> getImagePaths(Context context) {
        // The list of columns we're interested in:
        String[] columns = {MediaStore.Images.Media.DATA, MediaStore.Images.Media.DATE_ADDED};

        final Cursor cursor = context.getContentResolver().
                query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, // Specify the provider
                        columns, // The columns we're interested in
                        null, // A WHERE-filter query
                        null, // The arguments for the filter-query
                        MediaStore.Images.Media.DATE_ADDED + " DESC" // Order the results, newest first
                );

        List<String> result = new ArrayList<String>(cursor.getCount());

        if (cursor.moveToFirst()) {
            final int image_path_col = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
            do {
                result.add(cursor.getString(image_path_col));
            } while (cursor.moveToNext());
        }
        cursor.close();

        return result;
    }
}