AsyncTask(update) 仅在应用程序第一次打开时有效，但在 5 秒后不更新

Posted 2023-05-07

【中文标题】AsyncTask(update) 仅在应用程序第一次打开时有效，但在 5 秒后不更新

【英文标题】：AsyncTask(update) works only when app get opened first time, but it is not updating after 5 sec

【发布时间】：2017-02-07 00:05:39

【问题描述】：

此外，当我更改屏幕方向时，数据才会更新。 当我敬酒时，数据会在 5 秒后发生变化，但不知道为什么数据没有更新。onPreExecute() 每 5 秒后也会工作

1.这是我的 update.java 文件

public class update extends Activity implements LocationListener 
    protected String mLatitudeText;
    protected String mLongitudeText;
    protected String mCode = "1001";
    protected java.net.URL url;
    protected HttpURLConnection conn;
    android.os.Handler customHandler;
    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) 
        requestPermissions(new String[]android.Manifest.permission.ACCESS_FINE_LOCATION, 0);
        return;
    
    LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    lm.requestLocationUpdates(LocationManager.PASSIVE_PROVIDER, 5, 0, (android.location.LocationListener) this);
    Location mLastLocation = lm.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);

    mLatitudeText = (String.valueOf(mLastLocation.getLatitude()));
    mLongitudeText = (String.valueOf(mLastLocation.getLongitude()));

    final android.os.Handler handler = new android.os.Handler();
    Timer timer = new Timer();
    TimerTask backtask = new TimerTask() 
        @Override
        public void run() 
            handler.post(new Runnable() 
                public void run() 
                    try 
                        LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
                        Location mLastLocation = lm.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);

                        mLatitudeText = (String.valueOf(mLastLocation.getLatitude()));
                        mLongitudeText = (String.valueOf(mLastLocation.getLongitude()));
                        String[] s = new String[3];
                        s[0]=mCode;
                        s[1]=mLatitudeText;
                        s[2]=mLongitudeText;
                        Toast.makeText(getApplicationContext(), mLatitudeText + " and " + mLongitudeText, Toast.LENGTH_LONG).show();
                        makePOST.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,s);

                     catch (Exception e) 
                        // TODO Auto-generated catch block
                    
                
            );
        
    ;
    timer.schedule(backtask, 0, 5000);

    AsyncTask<String, Void, String> makePOST=new AsyncTask<String, Void, String>()
    protected void onPreExecute() 
        Toast.makeText(update.this, "onPreExecute", Toast.LENGTH_LONG).show();
    
    protected String doInBackground(String... params) 
            try 
                mCode=params[0];
                mLongitudeText=params[1];
                mLongitudeText=params[2];
                url = new URL("http://student.96.lt/Android/update.php");
                conn = (HttpURLConnection) url.openConnection();
                conn.setDoOutput(true);
                conn.setDoInput(true);
                conn.setRequestMethod("POST");
                String postdat = "code" + "=" + URLEncoder.encode(mCode, "UTF-8") + "&" + "latitude" + "=" + URLEncoder.encode(mLatitudeText, "UTF-8") + "&" + "longitude" + "=" + URLEncoder.encode(mLongitudeText, "UTF-8");
                //String postdat=mLatitudeText;
                conn.setFixedLengthStreamingMode(postdat.getBytes().length);
                conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
                OutputStream OS = conn.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(OS, "UTF-8"));
                bufferedWriter.write(postdat);
                bufferedWriter.flush();
                // Get output
                bufferedWriter.close();
             catch (java.net.MalformedURLException ex) 
                //Toast.makeText(this, ex.toString(), duration ).show();
             catch (java.io.IOException ex) 
                //Toast.makeText(this, ex.toString(), duration).show();
            
            return null;
        

    ;
@Override
    public void onLocationChanged (Location location)



    

    @Override
    public void onProviderDisabled (String provider)
        // TODO Auto-generated method stub

    

    @Override
    public void onProviderEnabled (String provider)
        // TODO Auto-generated method stub

    

    @Override
    public void onStatusChanged (String provider,int status, Bundle extras)
        // TODO Auto-generated method stub

    

请帮帮我，我还处于初级阶段。

【问题讨论】：

所以您无法将最新的纬度和经度位置更新到您的服务器，因为“doInBackground”无法正常工作？

请告诉我该怎么做？

我正在尝试了解您的问题..您无法实现什么？

你的意思是什么 - “当我改变屏幕方向时，只有数据才会更新。” ?你想在哪里更新数据？在你的 UI 线程或服务器中？

【参考方案1】：

一个任务只能运行一次。要再次运行相同的代码，您需要创建一个新的 AsyncTask 对象。它会抛出一个异常来告诉您这一点，但您忽略了所有异常（通常是个坏主意）。

【讨论】：

那我该怎么办？请帮帮我

创建一个新的 AsyncTask。现在您正在创建 1 并将其存储在值 makePost 中。相反，每次都通过 new 分配一个新的。

你能告诉我怎么做吗？如果你输入几行代码会更好