我試圖從URL接收JSON。在獲得對象後,我將解析它並將其加載到我的應用程序的列表視圖中。我使用Adapter來創建列表視圖並在mainActivity上運行我的jsonTask,然後將結果傳遞給適配器。它總是拋出空指針異常。有沒有更好的方法來做到這一點?我是新來的android和json任務運行async如何使我的用戶界面加載等待jsonTask的結果。這是我的代碼;Android異步JsonTask錯誤
主要活動;
public class TvActivity extends Activity {
ListView lv;
ArrayList<TV> tvList;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context = this;
new JSONTask().execute();
lv = (ListView) findViewById(R.id.listView);
lv.setAdapter(new Adapter(this, tvList));
}
}
public class JSONTask extends AsyncTask<String, String, JSONArray> {
ProgressDialog pDialog;
@Override
protected JSONArray doInBackground(String... params) {
return Utility.getJSONArray(Constants.TV_JSON_URL);
}
@Override
protected void onPostExecute(JSONArray result) {
pDialog.dismiss();
for (int i = 0; i < result.length(); i++) {
try {
JSONObject row = result.getJSONObject(i);
String title = row.getString(Constants.TV_TITLE);
String code = row.getString(Constants.TV_CODE);
String image_url = row.getString(Constants.TV_IMAGE_URL);
tvList.add(new TV(title, image_url, code));
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
My Adapter;
public class TvAdapter extends BaseAdapter {
String[] result;
Context context;
ArrayList<TV> tvArrayList;
int[] imageId;
private static LayoutInflater inflater = null;
public TvAdapter(TvActivity mainActivity, ArrayList<TV> tvList) {
// TODO Auto-generated constructor stub
//result = prgmNameList;
context = mainActivity;
tvArrayList = tvList;
//imageId = prgmImages;
inflater = (LayoutInflater) context.
getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return tvArrayList.size();
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return tvArrayList.get(position);
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
public class Holder {
TextView tv;
ImageView img;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
TV tvItem = (TV) getItem(position);
Holder holder = new Holder();
View rowView;
rowView = inflater.inflate(R.layout.tv_list, null);
holder.tv = (TextView) rowView.findViewById(R.id.textView1);
holder.img = (ImageView) rowView.findViewById(R.id.imageView1);
holder.tv.setText(tvItem.getTitle());
// holder.img.setImageResource(imageId[position]);
rowView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Toast.makeText(context, "You Clicked " + tvItem[position], Toast.LENGTH_LONG).show();
}
});
return rowView;
}
}
這是很難知道你的問題,而這是解決的堆棧跟蹤 –
。感謝您的每一個評論和答案。 –