1.声明 GridView

 private PullToRefreshGridView ptrgv;

2.为 GridView 添加图片

        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {
            ViewHolder vh;         
            if (view == null) {
                view = LayoutInflater.from(ctx).inflate(R.layout.list_item_for_gridview, null);
                vh = new ViewHolder();
                vh.iv = (ImageView) view.findViewById(R.id.imageView_cen);
                view.setTag(vh);
            }
            vh = (ViewHolder) view.getTag();
            Picture pic = pictures.get(i);

            //用OkhttpUtils        compile 'com.zhy:okhttputils:2.6.2'
            final ViewHolder finalVh = vh;
            OkHttpUtils
                    .get()
                    .url("https://www.baidu.com/img/bd_logo1.png")
                    .build()
                    .execute(new BitmapCallback() {
                        @Override
                        public void onError(okhttp3.Call call, Exception e, int id) {
                        }

                        @Override
                        public void onResponse(Bitmap response, int id) {
                            finalVh.iv.setImageBitmap(response);                           
                        }
                    });    
            return view;
        }

        static class ViewHolder {
          ImageView iv;
          public ImageView getIv() {
                return iv;
            }
        }

3.为 GridView 设置点击事件

        ptrgv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                imageView = (ImageView) findViewById(R.id.imageView_cen);
                Toast.makeText(MainActivity.this,"jaja",Toast.LENGTH_SHORT).show();
                Intent intent = new Intent(MainActivity.this,ItemLayout.class);

                byte[] mypic = null;
                imageView.setDrawingCacheEnabled(true);
                Bitmap bitmap = imageView.getDrawingCache();
                mypic = Bitmap2Bytes(bitmap);
                intent.putExtra("picture",mypic);
                startActivity(intent);
            }
        });

4.将 Bitmap 转换为 Bytes

 private byte[] Bitmap2Bytes(Bitmap bitmap){
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.PNG,100,byteArrayOutputStream);
        return byteArrayOutputStream.toByteArray();
    }

5.设置另一个 Activity

public class ItemLayout extends AppCompatActivity {

    private ImageView imageView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_item_layout);
        imageView = (ImageView) findViewById(R.id.imageview33);
        Intent intent = getIntent();
        if(intent != null){
            byte [] mypics = intent.getByteArrayExtra("picture");
            Bitmap bitmap = BitmapFactory.decodeByteArray(mypics,0,mypics.length);
            imageView.setImageBitmap(bitmap);
        }
    }

    private byte[] Bitmap2Bytes(Bitmap bitmap){
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.PNG,100,byteArrayOutputStream);
        return byteArrayOutputStream.toByteArray();
    }
}

6.另一个 Avtivity 的 Layout

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/imageView_cen"/>

</LinearLayout>