java - 如何卡住代码直到收到 volley 请求的响应？

Question

我正在尝试从另一个类调用此方法；在服务器上检查用户 ID 和密码后，它应该返回 true 或 false。

即使登录过程成功，它也总是返回false，因为在我收到请求响应之前它返回默认值false!

在发布这个问题之前我进行了大量搜索，但对于如何解决这个问题没有明确的答案。

MyHelper myHelper = new MyHelper();
myHelper.setVolleyResponseListener(new MyHelper.OnVolleyResponse()
{
    @Override
    public void onResponse(JSONObject jsonObject)
    {
        // do watever you want here with response.
    }
});

if (myHelper.doBackgroundLogin(getApplicationContext())) {
    uploadImageToServer();
}else{
    finish();
    startActivity(new Intent(AccountProfileImageActivity.this, AccountLoginActivity.class));
}

<小时/>

package com.company.testApp;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.View;
import android.view.WindowManager;
import android.widget.Toast;

import com.android.volley.AuthFailureError;
import com.android.volley.DefaultRetryPolicy;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;

/**
 * Created by Aly on 1/11/2017.
 */

public class MyHelper {

    private static AlertDialog.Builder builder;
    public static Context ctx;
    public static ValuesManager vm;

    public static boolean status = false;


    public static boolean doBackgroundLogin(final Context context) {
        vm = new ValuesManager( context, context.getString(R.string.saved_values_file_name) );
        String user_email = vm.retrieveSharedPreferences("user_email");
        String user_password = vm.retrieveSharedPreferences("user_password");

        Toast.makeText(context, user_email + " - " + user_password, Toast.LENGTH_SHORT).show();
        //------------------------------------------------------------------------------------------
//        final MyProgressDialog progressDialog;
//        progressDialog = MyProgressDialog.show(context, "title", "message");
//        //------------------------------------------------------------------------------------------
        String url =  context.getString(R.string.server_path);
        Log.d("URL : ", url);
        StringRequest stringRequest = new StringRequest(Request.Method.POST,
                url,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        Log.i("response : ", response); // log the error to trace it and print message to user
//                        progressDialog.dismiss();
                        try {
                            JSONObject jsonObject = new JSONObject(response);
                            JSONArray jsonArray = jsonObject.getJSONArray("server_response");
                            JSONObject JO = jsonArray.getJSONObject(0);
                            String code = JO.getString("code");
                            if( code.equals("login_true") ) {
                                status = true;
                                vm.saveSharedPreferences( "user_token", JO.getString("user_token") );
                                Log.d("trace","code = " + code);
                                Log.d("trace","statusUpdated = " + status);
                            }
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Log.d("vERROR : ", error.toString()); // log the error to trace it and print message to user
//                        progressDialog.dismiss();
                    }
                }
        )
        {
            @Override
            protected Map<String, String> getParams() throws AuthFailureError {
                Map<String, String> params = new HashMap<>();
                params.put("action","account_login");
                params.put("email_address",vm.retrieveSharedPreferences("user_email"));
                params.put("password",vm.retrieveSharedPreferences("user_password"));
                return params;
            }
        };

        stringRequest.setRetryPolicy(new DefaultRetryPolicy(
                100000,
                DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
                DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
        MySingleton.getInstance(context).addToRequestQueue(stringRequest);
        //------------------------------------------------------------------------------------------
        Log.d("trace","status = " + status);
        return status;
   } 

    public interface OnVolleyResponse
    {
        void onResponse(JSONObject jsonObject);
    }

    public void setVolleyResponseListener(OnVolleyResponse responseListener)
    {
        this.volleyResponse = volleyResponse;
    }

}

Answer 1

您必须为此使用接口(interface)回调。

为什么？

因为这是异步调用，并且在不同的线程上工作。所以你的主线程不会等待它的结果。

解决方案

1. 在 MyHelper 类中创建接口(interface)

编辑

    OnVolleyResponse  onVolleyResponse;
    public interface OnVolleyResponse
    {
        void onResponse(JSONObject jsonObject);
    }

创建回调的setter方法

public void setVolleyResponseListener(OnVolleyResponse responseListener)
{
    this.volleyResponse = volleyResponse;
}

现在从您的Activity调用此方法

MyHelper myHelper = new MyHelper();
myHelper.setVolleyResponseListener(new OnVolleyResponse()
{
    @Override
    public void onResponse(JSONObject jsonObject)
    {
       // do watever you want here with response. 
    }
});
if (myHelper.doBackgroundLogin(getApplicationContext())) {
                            uploadImageToServer();
                        }else{
                            finish();
                            startActivity(new Intent(AccountProfileImageActivity.this, AccountLoginActivity.class));
                        }

注意

从 doBackgroundLogin 方法中删除静态，并使用 MyHelper 实例调用它。