android - 使用 AsyncTask 在 Android 4.2 中使用 JSON 填充 Spinner

Question

我目前正在尝试将我在 API10 中创建的应用程序的 MainActivity 代码转换为 API 16。根据我所阅读的内容，我必须开始使用 ASyncTask 来访问 URI 并在我的应用程序上显示信息。我设法在 2.3 中做到了这一点，但在将其转换为 JSON 后，我现在面临一些障碍。

从本质上讲，该应用程序所做的是，它需要一个 list 代码，即 WAMF33000，然后单击一个按钮，Spinner 就会填充该 list 中包含的作业。由于我对 ASyncTask 的概念相当陌生，因此我想了解我的代码如何应用于 ASyncTask 背后的理论。

根据我的代码，我有一些问题:-i) 我在 ASyncTask 中的哪个代码是传递的参数？ii) 我的 AsyncTask 中的进度值是多少？iii) 最后，我的返回值是 ManifestItems 的 ArrayList 吗？

从 2.3 版本开始，我调用了 JSON 两次 - 一次是在 list 中加载 cargo ，第二次是加载在微调器中选择的 cargo 的详细信息。

以下是我的代码:

package com.signonglass;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;


import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import org.json.*;

import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.telephony.TelephonyManager;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity
{
    private final static String POD_URI = "http://192.168.0.105:8092/PodCore.svc";
    private EditText evManifestCode;
    private Spinner list_job;
    private Button btnSubmit;
    private String jobName;
    private Button btnCons;
    ArrayList<ManifestItemObj> jobList = new ArrayList<ManifestItemObj>();
    ArrayList<ConsignmentItems> conItemList = new ArrayList<ConsignmentItems>();
    Consignments retConsignment;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        evManifestCode = (EditText)findViewById(R.id.manifest);
        btnSubmit = (Button)findViewById(R.id.btnSearchManifest);
        list_job = (Spinner)findViewById(R.id.jobSpinner);
        //tvView = (TextView)findViewById(R.id.deviceIdt);



        //TelephonyManager telephonyManager = (TelephonyManager) this.getSystemService(Context.TELEPHONY_SERVICE);
        //String IMEI_Number = telephonyManager.getDeviceId();
        //tvView.setText("IMEI Number: " + IMEI_Number);

    }

    public class MyAsyncTask extends AsyncTask<String, Void, ArrayList<ManifestItemObj>>
    {

        protected void onPreExecute()
        {

        }

        protected void onPostExecute(ArrayList<ManifestItemObj> jobList)
        {

        }

        @Override
        protected ArrayList<ManifestItemObj> doInBackground(String... params)
        {
            //http get request
            HttpGet request = new HttpGet(POD_URI + "/getJobs/" + evManifestCode.getText().toString());
            //set the hedear to get the data in JSON format
            request.setHeader("Accept", "application/json");
            request.setHeader("Content-type", "application/json");

            DefaultHttpClient client = new DefaultHttpClient();
            String theString = new String("");

            try
            {
                //get the response
                HttpResponse response = client.execute(request);
                HttpEntity entity = response.getEntity();
                InputStream is = entity.getContent();
                BufferedReader reader = new BufferedReader(new InputStreamReader(is));

                StringBuilder builder = new StringBuilder();
                String line;
                while ((line = reader.readLine()) != null) {
                                builder.append(line);
                        }
                is.close();
                theString = builder.toString();

                JSONObject jobsJSON = new JSONObject(theString);
                JSONArray jobs = jobsJSON.getJSONArray("getJobsResult");

                for(int i = 1; i < jobs.length(); i++)
                {
                    JSONObject mit = jobs.getJSONObject(i);
                    ManifestItemObj mi = new ManifestItemObj();
                    mi.ManifestItemID = mit.getInt("ManifestItemID");
                    mi.JobType = mit.getString("JobType");
                    mi.FKID = mit.getInt("FKID");
                    jobList.add(mi);
                }      
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
            return jobList;
        }
    }


    /*private void showToast(String msg)
    {
        // TODO Auto-generated method stub
        Toast.makeText(this, "Toast: " + msg, Toast.LENGTH_LONG).show();
    }*/

    public void onViewConsignment(View view)
    {
        ShowItemsOfManifest(retConsignment);
    }

    public Consignments getConsignmentManifest(String consignment)
    {
        Consignments con = new Consignments();

        try
        {
            DefaultHttpClient client = new DefaultHttpClient();
            String theString = new String("");
            //http get request
            HttpGet request = new HttpGet(POD_URI + "/getJobDetails/" + consignment);
            //set the hedear to get the data in JSON format
            request.setHeader("Accept", "application/json");
            request.setHeader("Content-type", "application/json");

            //get the response
            HttpResponse response = client.execute(request);
            HttpEntity entity = response.getEntity();
            InputStream is = entity.getContent();
            BufferedReader reader = new BufferedReader(new InputStreamReader(is));

            StringBuilder builder = new StringBuilder();
            String line;
            while ((line = reader.readLine()) != null)
            {
                builder.append(line);
            }
            is.close();

            theString = builder.toString();

            JSONObject conJSON = new JSONObject(theString);
            JSONArray cons = conJSON.getJSONArray("getJobDetailsResult");

            for(int i = 0; i < cons.length(); i++)
            {
                JSONObject cObj = cons.getJSONObject(i);
                con.ConsignmentID = cObj.getInt("ConsignmentID");
                con.ConsignmentCreationDate = cObj.getString("ConsignmentCreationDate");
                con.ConsignmentCustRef = cObj.getString("ConsignmentCustRef");
                con.OrderNo = cObj.getString("OrderNo");
                con.ConsignmentActive = cObj.getBoolean("ConsignmentActive");
                con.JobType = cObj.getString("JobType");

                //Client object
                JSONObject clObj = cObj.getJSONObject("Client");
                Clients cl = new Clients();
                cl.ClientId = clObj.getInt("ClientID");
                cl.ClientName = clObj.getString("ClientName");
                con.Clients = cl;

                //ShipTo object
                JSONObject stObj = cObj.getJSONObject("ShipTo");
                ShipTo sto = new ShipTo();
                sto.ShipToId = stObj.getInt("ShipToId");
                sto.ShipToName = stObj.getString("ShipToName");
                sto.ShipToAddress1 = stObj.getString("ShipToAddress1");
                sto.ShipToAddress2 = stObj.getString("ShipToAddress2");
                sto.ShipToCity = stObj.getString("ShipToCity");
                sto.ShipToPostcode = stObj.getString("ShipToPCode");
                sto.ShipToState = stObj.getString("ShipToState");
                con.ShipTo = sto;

                //FreightZone object
                JSONObject fzObj = cObj.getJSONObject("FreightZone");
                FreightZones fz = new FreightZones();
                fz.FreightZoneID = fzObj.getInt("FreightZoneId");
                fz.FreightZone = fzObj.getString("FreightZone");
                con.FreightZone = fz;

                JSONArray conItems = cObj.getJSONArray("ConsignmentItems");

                for(int m = 0; m < conItems.length(); m++)
                {
                    JSONObject cit = conItems.getJSONObject(m);
                    ConsignmentItems ci = new ConsignmentItems();
                    ci.ConsignmentItemID = cit.getInt("ConsignmentItemsID");
                    ci.Quantity = cit.getInt("QTY");

                    //get Product from ConsignmentItems
                    JSONObject pro = cit.getJSONObject("Products");
                    Products prod = new Products();
                    prod.ProductId = pro.getInt("ProductID");
                    prod.ProductModel = pro.getString("ProductModel");
                    prod.ItemsPerCarton = pro.getInt("PerCarton");
                    prod.ProductDescription = pro.getString("Description");
                    prod.Height = (float) pro.getDouble("Height");
                    prod.Length = (float) pro.getDouble("Length");
                    prod.Width = (float) pro.getDouble("Width");
                    prod.Cubic = (float) pro.getDouble("Cubic");
                    ci.Product = prod;
                    conItemList.add(ci);
                    con.ConsignmentItems = conItemList;
                }
            }
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        return con;
    }

    public void ShowItemsOfManifest(Consignments consignments)
    {
        Bundle bundle = new Bundle();
        Intent newIntent = new Intent(this.getApplicationContext(), ConActivity.class);
        newIntent.putExtras(bundle);
        newIntent.putExtra("Consignment", consignments);

        this.startActivity(newIntent);

    }

    public void onSearchClick(View view)
    {
        new MyAsyncTask().execute();
        ManifestItemAdapter mia = new ManifestItemAdapter(MainActivity.this, android.R.layout.simple_spinner_item, jobList);
        list_job.setAdapter(mia); 
    }
}

我期待通过您对我的代码提出的建设性意见进一步了解 ASyncTask。伙计们，在此先感谢您帮助我改进我的代码和我对 Android 的理解! :)

PS:如果您需要更多代码，请告诉我。我会根据需要更新我的帖子，提供更多信息。干杯!

Answer 1

AsyncTask 背后的要点是允许您在单独的线程上运行后台工作，例如网络内容，这样您就不会占用 UI，用户仍然可以在下载数据时做事。

Which of my code in the ASyncTask is the parameter that is being passed?

您目前没有将任何params 传递给AsyncTask

new MyAsyncTask().execute(); // you would put params in here if needed such as a URL, String, etc...

What is the progress value in my AsyncTask?

据我所知，你没有。如果您愿意，您可以使用 publishProgress(value) 并将其发送到 onProgressUpdate() 以更新下载的文件、进度时间、剩余时间等内容。 ..

Finally, is my return value the ArrayList of ManifestItems?

您正在返回 jobList，因此它将被发送到 onPostExecute() 以执行您需要的操作

注意:了解AsyncTask 最重要的事情之一是您不能从doInBackground 更新UI () 因此您必须在其他 AsyncTask 方法之一中执行此操作或将值传回 UI 函数。此外，AsyncTask 在 2.3 中的工作方式与在 3.0 及更高版本中的不同。它们不再并行运行，而是放入队列中。因此，如果您希望它们在 4.2 中并行运行，您可能需要阅读有关 executeOnExecutor() 的内容。我希望这能回答你的问题

AsyncTask

executeOnExecutor()(http://developer.android.com/reference/android/os/AsyncTask.html#executeOnExecutor(java.util.concurrent.Executor，参数...)

我看到的其他一些事情是您需要将 @Override 注释添加到已实现的方法以及 super 调用中。