我在我的应用程序中使用 StackExchange API,它返回如下响应:
{
"items":[
{
"tags":[
"android",
"gridview",
"android-fragments",
"android-activity"
],
"owner":{
"reputation":30,
"user_id":3303863,
"user_type":"registered",
"profile_image":"http://i.stack.imgur.com/44pCy.jpg?s=128&g=1",
"display_name":"chris.b",
"link":"http://stackoverflow.com/users/3303863/chris-b"
},
"is_answered":false,
"view_count":7,
"answer_count":0,
"score":0,
"last_activity_date":1429979620,
"creation_date":1429979620,
"question_id":29867827,
"link":"http://stackoverflow.com/questions/29867827/android-app-close-without-error-on-click-of-the-first-gridview-item",
"title":"Android App Close without Error, on click of the first gridview Item"
},
{
"tags":[
"android",
"genymotion"
],
"owner":{
"reputation":61,
"user_id":213199,
"user_type":"registered",
"accept_rate":54,
"profile_image":"https://www.gravatar.com/avatar/2f0b0c0e0e449255b5e2892b10b97ba4?s=128&d=identicon&r=PG",
"display_name":"Stella",
"link":"http://stackoverflow.com/users/213199/stella"
},
"is_answered":false,
"view_count":7,
"answer_count":0,
"score":0,
"last_activity_date":1429979268,
"creation_date":1429979268,
"question_id":29867773,
"link":"http://stackoverflow.com/questions/29867773/unable-to-run-android-app-in-genymotion-emulator",
"title":"Unable to run Android app in Genymotion emulator"
},
我正在使用以下代码从 URL 获取字符串:
public String readJSON() {
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = null;
try {
response = client.execute(httpGet);
} catch (IOException e) {
e.printStackTrace();
}
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) {
HttpEntity entity = response.getEntity();
InputStream content = null;
try {
content = entity.getContent();
} catch (IOException e) {
e.printStackTrace();
}
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String line;
try {
while ((line = reader.readLine()) != null) {
builder.append(line);
}
} catch (IOException e) {
e.printStackTrace();
}
} else {
//Log.e(re.class.toString(), "Failed to download file");
}
return builder.toString();
}
我正在使用异步任务在文本视图中显示问题,如下所示:
public class JSONTask extends AsyncTask<String,String,JSONObject>
{
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Getting Data ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... params) {
try {
ob1 = new JSONObject(readJSON());
} catch (JSONException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
return ob1;
}
@Override
protected void onPostExecute(JSONObject jsonObject) {
try {
mJSONArr = jsonObject.getJSONArray("items");
for(int i=0;i<20;i++)
{
ob2 = mJSONArr.getJSONObject(i);
holder+=ob2.getString("title");
}
tv.setText(holder);
pDialog.dismiss();
} catch (JSONException e) {
e.printStackTrace();
}
}
}
但我收到一个错误消息
“尝试在空对象引用上调用虚拟方法 'org.json.JSONObject org.json.JSONArray.getJSONObject(int)'”
在这些线上:
mJSONArr = ob1.getJSONArray("items");
和
public class JSONTask extends AsyncTask<String,String,JSONObject>
我该如何解决?另外,如何从这个 JSON 响应中的“所有者”对象访问“显示名称”?
谢谢