在第一次从方法调用时,Volley返回null [英] Volley returns null on first call from method
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问题描述
我正在尝试使用齐射从服务器检索数据,但是当我第一次调用此方法时,我从服务器获得了响应,但是该方法返回null.如果我第二次打电话给我,则得到最后的答复.
I am trying to retrieve data from server using volley, but when I call this method the first time, I get the response from server, but null is returned by the method. If I call it the second time I get the last response.
public String retrieveDataFromServer(String url, String param, final String token){
StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
try{
data = new JSONObject(response).toString();
}catch (Exception e){}
//Toast.makeText(getApplicationContext(), "wow" + data, Toast.LENGTH_SHORT).show();
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
try{
data = new JSONObject(error.toString()).toString();
}catch (Exception e){}
//Toast.makeText(getApplicationContext(), "" +data, Toast.LENGTH_SHORT).show();
}
}) {
/**
* Passing some request headers
*/
@Override
public Map<String, String> getHeaders() throws AuthFailureError {
String bearer = "Bearer ".concat(token);
Map<String, String> headersSys = super.getHeaders();
HashMap<String, String> headers = new HashMap<String, String>();
headers.put("Content-Type", "application/json; charset=utf-8");
//headers.put("token", token);
headersSys.remove("Authorization");
headers.put("Authorization", bearer);
headers.putAll(headersSys);
return headers;
}
};
// Adding request to request queue
addToRequestQueue(stringRequest);
//Toast.makeText(getApplicationContext(), "wow" + data, Toast.LENGTH_SHORT).show();
return data;
}
如何在第一次调用方法时得到响应?
How do I get the response on first call of method?
推荐答案
您可以使用回叫来返回Volley响应:
You can use call back to return Volley response:
public void retrieveDataFromServer(final VolleyCallback callback) {
StringRequest strReq = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
callback.onSuccess(response);
}
}
}}
创建界面:
public interface VolleyCallback{
void onSuccess(String response);
}
从活动中获取结果:
String yourString = "";
@override
public void onResume() {
super.onResume();
retrieveDataFromServer(new VolleyCallback(){
@Override
public void onSuccess(String response){
//Get result from here
yourString = response;
}
});
}
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