title: Flutter GridTile can be triggered with tap?
body: <p>I have created a flutter app and used the image-picker to get images to the center as a gridView with looping the image array with grid tiles.Is it possible to trigger the gridTile when it is tapped?
  Below is the code from the main.dart for getting the image adding it to an array and to a grid view.</p>
  
  <pre><code>class _MyHomePageState extends State&lt;MyHomePage&gt; {
  int _counter = 0;
  File _imageFile;
  List&lt;File&gt; _imageList=[];
  
  getImage() async {
  var _fileName = await ImagePicker.pickImage();
  setState(() {
    _imageFile = _fileName;
    _imageList.add(_imageFile);
  });
  }
  
   removeImage(int index){
    setState((){
    _imageList.removeAt(index);
  });
  }
   @override
   Widget build(BuildContext context) {
  
   return new Scaffold(
    appBar: new AppBar(
  
      title: new Text(widget.title),
    ),
    body: new Center(
  
      child:_imageList.length == 0
          ? new Text('No image selected.')
          :new GridView.count(
          crossAxisCount: 4,
          childAspectRatio: 1.0,
          padding: const EdgeInsets.all(4.0),
          mainAxisSpacing: 4.0,
          crossAxisSpacing: 4.0,
          children: _imageList.map((File file) {
            return new GridTile(
  
                child: new Image.file(file, fit: BoxFit.cover,));
  
          }).toList()),
    ),
  
    floatingActionButton: new FloatingActionButton(
      onPressed:getImage,
      tooltip: 'Pick Image',
      child: new Icon(Icons.add_a_photo),
    ),
  );
  }
  }
  </code></pre>