我試圖返回 arrayList ，當我返回 arrayList 為空時。當我返回 arrayList 但它不起作用時，我將使用它。 public ArrayList<Cities> getCities(){ final ArrayList<Cities> cities=new ArrayList<>(); String url = "http://10.0.2.2:3000/cities"; mQueue = Volley.newRequestQueue(context); JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, null, new Response.Listener<JSONObject>() { @Override public void onResponse(JSONObject response) { try { JSONArray jsonArray = response.getJSONArray("city"); for (int i = 0; i < jsonArray.length(); i++) { JSONObject city = jsonArray.getJSONObject(i); String id = city.getString("_id"); String name = city.getString("name"); Cities p=new Cities(id,name); cities.add(p); } } catch (JSONException e) { e.printStackTrace(); } } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { error.printStackTrace(); } }); mQueue.add(request);return cities;}
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搖曳的薔薇
TA貢獻1793條經驗 獲得超6個贊
如果您的響應返回一個帶有城市元素數組的 JSONObject，那么您的請求是正確的，但如上所述，在調用回調之前，您不能期望實際得到結果。這是一個使用返回 JSONArray 的 JSONArrayRequest 的示例，但在您從 JSONObject 中提取 City 數組后，其工作方式與您的幾乎相同。
private ListView mTripList;
public ArrayList<TripItem> tripItems;
private JSONArray unclaimedTrips;
private TripSelectAdapter adapter;
public void getTrips() {
JsonArrayRequest req = new JsonArrayRequest(url, new Response.Listener<JSONArray> () {
@Override
public void onResponse(JSONArray response) {
// Public Array
unclaimedTrips = response;
tripItems = new ArrayList<TripItem>();
// Optional if you want to manipulate the data in some way
if (unclaimedTrips != null) {
for (int i = 0; i < unclaimedTrips.length(); i++) {
try {
JSONObject item = unclaimedTrips.getJSONObject(i);
int tripID = item.getInt("trip_id");
int claimID = item.getInt("claim_id");
String payrollCode = item.getString("payroll_code");
String tripDate = item.getString("trip_date");
String tripPurpose = item.getString("trip_purpose");
TripItem tripItem = new TripItem(tripID, claimID, payrollCode, tripDate, tripPurpose);
tripItems.add(tripItem);
} catch (JSONException e) {
e.printStackTrace();
}
}
refreshData();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
unclaimedTrips = null;
refreshData();
}
}) {
@Override
public Map<String, String> getHeaders() throws AuthFailureError {
HashMap<String, String> headers = new HashMap<String, String>();
headers.put("Accept", "application/json");
headers.put("Content-Type", "application/json");
return headers;
};
};
// add the request object to the queue to be executed
MyApplication.getInstance().addToRequestQueue(req);
}
public void refreshData() {
if (tripItems.isEmpty()) {
mEmptyList.setVisibility(android.view.View.VISIBLE);
} else {
mEmptyList.setVisibility(android.view.View.GONE);
}
adapter = new TripSelectAdapter(this, thisContext, tripItems);
mTripList.setAdapter(adapter);
}
皈依舞
TA貢獻1851條經驗 獲得超3個贊
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