how to use gridview in onPostexecute AsyncTask

问题

i have following code , i want image load first from drawable folder and after api. image successfully load from drawable folder using getData() method, but i don't know how to load image from url and update gridview. onPostExecute method when i update my grid below comment line crash the application that's why i comment my gridview code in method onPostExecute method please check and help me this

I am New in Android please show example

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;
    }
}
}

when i check in log using below method its shows json data

 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"
        }
     ]

回答1:

Add a new method in your adapter class like this

public class GridViewAdapter extends BaseAdapter{

    private ArrayList<ImageItem> mItemList;

    public void updateItemList(ArrayList<ImageItem> newItemList){
        this.mItemList = newItemList;
        notifyDataSetChanged();
    }

}

and onPostExecute call this methode and set new list. So your onPost looks like this

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);
            gridAdapter.updateItemList(getData());         


        }

To load imagview using url you can use Picasso Library , for your refrence it looks like this

Picasso.with(context).load("http://i.imgur.com/DvpvklR.png").into(imageView);

add following dependency to use picasso

compile 'com.squareup.picasso:picasso:2.5.2'

来源：https://stackoverflow.com/questions/47617365/how-to-use-gridview-in-onpostexecute-asynctask