如何在AsyncTask中调用GridView并从url加载图像

Question

我有以下代码，我希望首先从drawable文件夹和api之后加载图像。 图像使用getData（）方法从可绘制文件夹成功加载， 但我不知道如何从网址加载图片并更新gridview 。 onPostExecute 方法，当我在评论行下面更新我的网格时崩溃应用程序，这就是我在方法 onPostExecute 方法中评论我的gridview代码的原因请检查并帮助我

  

我是Android新手请展示示例

public class MainActivity extends AppCompatActivity  {
    private GridView gridView;
    private GridViewAdapter gridAdapter;

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

      gridView = (GridView) findViewById(R.id.gridView);
      gridAdapter = new GridViewAdapter(this, R.layout.grid_item_layout, getData());
        gridView.setAdapter(gridAdapter);
        APICaller ob = new APICaller();
        ob.execute();
        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
                ImageItem item = (ImageItem) parent.getItemAtPosition(position);

                //Create intent
                Intent intent = new Intent(MainActivity.this, abc.class);
                intent.putExtra("title", item.getTitle());
                intent.putExtra("image", item.getImage());

                //Start details activity
                startActivity(intent);
            }
        });
    }

    /**
     * Prepare some dummy data for gridview
     */
    private ArrayList<ImageItem> getData() {
        final ArrayList<ImageItem> imageItems = new ArrayList<>();
        TypedArray imgs = getResources().obtainTypedArray(R.array.image_ids);
        for (int i = 0; i < imgs.length(); i++) {
            Bitmap bitmap = BitmapFactory.decodeResource(getResources(), imgs.getResourceId(i, -1));
            imageItems.add(new ImageItem(bitmap, "Image#" + i));
        }
        return imageItems;
    }

    private ArrayList<ImageItem> getData(appmodel[] data) {
        Toast.makeText(getApplicationContext(),
                data.toString(), Toast.LENGTH_LONG).show();
        final ArrayList<ImageItem> imageItems = new ArrayList<>();
        TypedArray imgs = getResources().obtainTypedArray(R.array.image_ids);
        for (int i = 0; i < imgs.length(); i++) {
            Bitmap bitmap = BitmapFactory.decodeResource(getResources(), imgs.getResourceId(i, -1));
            imageItems.add(new ImageItem(bitmap, "Image#" + i));
        }
        return imageItems;
    }

class APICaller extends  AsyncTask{

        protected  void onPostExecute(Object result)
        {
          String data = (String)result;       
            Gson g = new Gson();
            Type t = new TypeToken<appmodel[]>(){}.getType();
            appmodel[] appm = (appmodel[])g.fromJson(data,t);
        //  gridView = (GridView) findViewById(R.id.gridView);
     //       gridAdapter = new GridViewAdapter(getApplicationContext(), R.layout.grid_item_layout, getData());
     //     gridView.setAdapter(gridAdapter);            


        }
    @Override
    protected Object doInBackground(Object[] objects) {

        HttpClient client = new DefaultHttpClient();
        HttpGet getlish =  new HttpGet("http://test.abc.com/api/test");
        ResponseHandler<String> handler = new BasicResponseHandler();
        Object result = new Object();
        try {
            result = client.execute(getlish,handler);
        }
        catch(Exception e)
        {


        }
        return result;
    }
}
}

当我使用下面的方法检查日志时，它显示了json数据

 protected  void onPostExecute(Object result)
        {
          String data = (String)result;       
            Log.d("myTag", data);
}

JSON

  [ {
        "apptype": 1,
        "imagename": "test",
        "imageurl": "http://test.abc.com/androidimages/test/test.jpg"
        }
     ]