从网格视图android studio保存图像

如何将从gridView（操作栏上）选择的图像保存到设备库中

这是我的代码：

画廊活动

public class GalleryActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_gallery);
        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() {
                    @Override
                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                        Intent intent = new Intent(GalleryActivity.this, ViewImageActivity.class);
                        //int item =(int) parent.getSelectedItemPosition();
                        intent.putExtra("id", position);


                        startActivity(intent);

                        // Toast.makeText(GalleryActivity.this,"" + position,Toast.LENGTH_SHORT).show();
                    }
                });


            }

            public class ImageAdapter extends BaseAdapter {
                private Context mContext;

                public ImageAdapter(GalleryActivity context) {
                    mContext = context;
                }

                public ImageAdapter() {

                }

                public int getCount() {
                    return mThumbIds.length;
                }

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

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

                public View getView(int position, View convertView, ViewGroup parent) {
                    ImageView imageView;
                    if (convertView == null) {
                        // if it's not recycled, initialize some attributes
                        imageView = new ImageView(mContext);

                        imageView.setLayoutParams(new GridView.LayoutParams(400, 400));
                        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                        imageView.setPadding(8, 8, 8, 8);


                    } else {
                        imageView = (ImageView) convertView;
                    }

                    imageView.setImageResource(mThumbIds[position]);
                    return imageView;
                }

                public Integer[] mThumbIds = {

                        R.drawable.car,
                        R.drawable.wolf,
                        R.drawable.dolphin,
                        R.drawable.cat,
                        R.drawable.car,
                        R.drawable.car,


                };


            }
    @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 ViewImageActivity extends GalleryActivity {

    ImageAdapter imageAdapter = new ImageAdapter(this);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_view_image);
        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();
            }
        });


        Intent i = getIntent();
        int position = i.getExtras().getInt("id");


        ImageAdapter imageAdapter = new ImageAdapter(this);
        ImageView imageView = (ImageView) findViewById(R.id.image);
        imageView.setImageResource(imageAdapter.mThumbIds[position]);


    }


}