如何在onPostexecute AsyncTask中使用gridview [英] how to use gridview in onPostexecute AsyncTask

问题描述

我有以下代码，我想首先从drawable文件夹中加载图像，然后从api中加载图像. 使用getData()方法成功从可绘制文件夹中加载图片， 但我不知道如何从url加载图像并更新gridview .当我在注释行下更新网格时， onPostExecute 方法使应用程序崩溃，这就是为什么我在方法 onPostExecute 方法中注释网格视图代码的原因，请检查并帮助我

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

我是Android的新手，请显示示例

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;
    }
}
}

当我使用以下方法检查日志时，它会显示json数据

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"
        }
     ]

推荐答案

在适配器类中添加这样的新方法

public class GridViewAdapter extends BaseAdapter{

    private ArrayList<ImageItem> mItemList;

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

}

和onPostExecute调用此方法并设置新列表.所以您的onPost看起来像这样

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());         


        }

要使用url加载imagview，您可以使用Picasso Library，其外观如下所示

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);

添加以下依赖项以使用毕加索

add following dependency to use picasso

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

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