我想构建一个Utils类，使Volley调用更简单，如下所示：
Utils.java：
public class Utils {
static JsonObjectRequest mJsonObjectRequest;
protected static boolean busy = true;
public static JSONObject makeJsonObjectRequest(Context context, int method, String url){
final JSONObject[] jsonObject = new JSONObject[1];
mJsonObjectRequest = new JsonObjectRequest
(method, url, null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
jsonObject[0] = response;
busy = false;
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
// TODO Auto-generated method stub
try {
jsonObject[0] = new JSONObject(error.toString());
} catch (JSONException e) {
e.printStackTrace();
}
busy = false;
}
});
// Access the RequestQueue through your singleton class.
VolleySingleton.getInstance(context).addToRequestQueue(mJsonObjectRequest);
while (true) {
if (!busy) break;
}
return jsonObject[0];
}
}
MainActivity.java：
JSONObject jsonObject = Utils.makeJsonObjectRequest(this, Request.Method.GET, url);
mTxtDisplay.setText("Response: " + jsonObject.toString());
当app运行时，jsonObject始终为null。我想询问是否可以延迟在makeJsonObjectRequest中返回jsonObject [0]，直到调用onResponse。我可以这样做吗？
答案 0 :(得分：2)
如果在后台线程上执行makeJsonObjectRequest，则可以通过以下方式执行同步Volley请求：
Can I do a synchronous request with volley?
如果您在UI线程上执行makeJsonObjectRequest，那么您不应该等待onResponse以避免阻止UI线程。在这种情况下使用回调。
答案 1 :(得分：1)
我创建了这个并按照以下方式管理，请看一下，希望它对您有用
public class APIManager {
public static void createRequest(Context c, String requestTag,
String endPoint, List<NameValuePair> params,
final OnRequestCompletedListener listener,
TransParentProgressDialog pd) {
ServerDetails serverDetails = new ServerDetails(c, endPoint, params);
JsonObjectRequest request = new JsonObjectRequest(Method.GET,
serverDetails.getQueryUrl(), null,
new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
listener.onRequestCompleted(response);
}
}, getErrorListener(c, pd)) {
};
AppController.getInstance().addToRequestQueue(request, requestTag);
}
public static ErrorListener getErrorListener(final Context c,
final TransParentProgressDialog pd, final TextView tvEmpty,
final String errorText) {
Response.ErrorListener listener = new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
if (pd != null && pd.isShowing()) {
pd.dismiss();
}
if (tvEmpty != null) {
tvEmpty.setText(errorText);
}
MyDialog dialog;
Log.d("volley-error", error.toString());
if (error instanceof TimeoutError) {
dialog = new MyDialog(c, "Server Timeout");
dialog.show();
return;
} else if (error instanceof NoConnectionError) {
dialog = new MyDialog(c, "No Connection or Invalid Url");
dialog.show();
return;
} else if (error instanceof ServerError) {
NetworkResponse response = error.networkResponse;
if (response != null) {
// int statusCode = response.statusCode;
byte[] data = response.data;
if (data != null) {
String str = new String(data);
try {
JSONObject object = new JSONObject(str);
Log.d("error response", object.toString());
if (object.has("errors")) {
JSONArray errors = object
.getJSONArray("errors");
JSONObject errorObject = errors
.getJSONObject(0);
dialog = new MyDialog(c, "Error!",
errorObject.getString("message"));
dialog.show();
} else {
dialog = new MyDialog(c, "Error!",
object.toString());
dialog.show();
}
} catch (JSONException e) {
e.printStackTrace();
dialog = new MyDialog(c, "Error!", "Error");
dialog.show();
}
} else {
dialog = new MyDialog(c, "Server Error");
dialog.show();
}
} else {
dialog = new MyDialog(c, "Server Error");
dialog.show();
}
} else if (error instanceof NetworkError) {
NetworkResponse response = error.networkResponse;
if (response != null) {
// int statusCode = response.statusCode;
byte[] data = response.data;
if (data != null) {
String str = new String(data);
try {
JSONObject object = new JSONObject(str);
Log.d("error response", object.toString());
if (object.has("errors")) {
JSONArray errors = object
.getJSONArray("errors");
JSONObject errorObject = errors
.getJSONObject(0);
dialog = new MyDialog(c, "Error!",
errorObject.getString("message"));
dialog.show();
} else {
dialog = new MyDialog(c, "Error!",
object.toString());
dialog.show();
}
} catch (JSONException e) {
e.printStackTrace();
dialog = new MyDialog(c, "Error!", "Error");
dialog.show();
}
} else {
dialog = new MyDialog(c, "Network Error");
dialog.show();
}
} else {
dialog = new MyDialog(c, "Network Error");
dialog.show();
}
} else if (error instanceof ParseError) {
dialog = new MyDialog(c, "Parse Error");
dialog.show();
} else if (error instanceof AuthFailureError) {
NetworkResponse response = error.networkResponse;
if (response != null) {
// int statusCode = response.statusCode;
byte[] data = response.data;
if (data != null) {
String str = new String(data);
try {
JSONObject object = new JSONObject(str);
Log.d("error response", object.toString());
if (object.has("errors")) {
JSONArray errors = object
.getJSONArray("errors");
JSONObject errorObject = errors
.getJSONObject(0);
dialog = new MyDialog(c, "Error!",
errorObject.getString("message"));
dialog.show();
} else {
dialog = new MyDialog(c, "Error!",
object.toString());
dialog.show();
}
} catch (JSONException e) {
e.printStackTrace();
dialog = new MyDialog(c, "Error!", "Error");
dialog.show();
}
} else {
dialog = new MyDialog(c, "Error!", "Error");
dialog.show();
}
} else {
dialog = new MyDialog(c, "Error connecting server");
dialog.show();
}
}
}
};
return listener;
}
}
完成请求回叫的界面是
public interface OnRequestCompletedListener {
public void onRequestCompleted(JSONObject response);
}
答案 2 :(得分：0)
感谢@Gennadii Saprykin和@Gopal Singh Sirvi的回答，我尝试了Callable和Interface Listener两种方式。然而，两者都有效，我更喜欢倾听者的方式。
OnRequestCompletedListener.java：
package com.example.volleyapp;
import org.json.JSONObject;
public interface OnRequestCompletedListener {
void onRequestCompleted(JSONObject response);
}
Utils.java：
package com.example.volleyapp;
import android.content.Context;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.concurrent.Callable;
public class Utils {
static JsonObjectRequest mJsonObjectRequest;
static Callable<Void> func=null;
public static void makeJsonObjectRequest_Listener(final Context context, final int method, final String url, final OnRequestCompletedListener listener){
mJsonObjectRequest = new JsonObjectRequest
(method, url, null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
listener.onRequestCompleted(response);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
// TODO Auto-generated method stub
try {
listener.onRequestCompleted(new JSONObject(error.toString()));
} catch (JSONException e) {
e.printStackTrace();
}
}
});
// Access the RequestQueue through your singleton class.
VolleySingleton.getInstance(context).addToRequestQueue(mJsonObjectRequest);
}
public static void makeJsonObjectRequest_Callable(final Context context, final int method, final String url, final MainActivity.JsonCallable doRequest){
mJsonObjectRequest = new JsonObjectRequest
(method, url, null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
try{
func = doRequest;
doRequest.jsonObject = response;
func.call();
} catch (Exception e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
// TODO Auto-generated method stub
try {
func = doRequest;
doRequest.jsonObject = new JSONObject(error.toString());
func.call();
} catch (JSONException e) {
e.printStackTrace();
}
}
});
// Access the RequestQueue through your singleton class.
VolleySingleton.getInstance(context).addToRequestQueue(mJsonObjectRequest);
}
}
MainActivity.java：
package com.example.volleyapp;
import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import org.json.JSONObject;
import java.util.concurrent.Callable;
public class MainActivity extends Activity {
JsonCallable jsonCallable=null;
TextView mTxtDisplay;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTxtDisplay = (TextView) findViewById(R.id.textView);
String url = "https://10.0.2.2/aspnet/webapi/products/1";
// Callable way
// jsonCallable = new JsonCallable();
// Utils.makeJsonObjectRequest_Callable(this, Request.Method.GET, url, jsonCallable);
// Listener way
OnRequestCompletedListener listener = new OnRequestCompletedListener() {
@Override
public void onRequestCompleted(JSONObject response) {
mTxtDisplay.setText(response.toString());
}
};
Utils.makeJsonObjectRequest_Listener(this, Request.Method.GET, url, listener);
}
class JsonCallable implements Callable {
public JSONObject jsonObject;
public JsonCallable(){
}
@Override
public Object call() throws Exception {
mTxtDisplay.setText(jsonObject.toString());
return null;
}
}
}
再次感谢大家的帮助！