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我正在尝试使用其他数据（用户当前的 SSID）更新我的数据库，但是在尝试保存数据库时 - 整个应用程序强制关闭。

我知道保存数据时会导致 NullPointer 异常 - 但我不知道我做错了什么导致它。

日志猫：

04-04 21:24:08.351: E/AndroidRuntime(10745): FATAL EXCEPTION: AsyncTask #2
04-04 21:24:08.351: E/AndroidRuntime(10745): java.lang.RuntimeException: An error occured while executing doInBackground()
04-04 21:24:08.351: E/AndroidRuntime(10745):    at android.os.AsyncTask$3.done(AsyncTask.java:299)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at java.util.concurrent.FutureTask.run(FutureTask.java:239)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at java.lang.Thread.run(Thread.java:856)
04-04 21:24:08.351: E/AndroidRuntime(10745): Caused by: java.lang.NullPointerException
04-04 21:24:08.351: E/AndroidRuntime(10745):    at com.app.gamedemo.AddEditDevice.saveContact(AddEditDevice.java:117)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at com.app.gamedemo.AddEditDevice.access$1(AddEditDevice.java:111)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at com.app.gamedemo.AddEditDevice$1$1.doInBackground(AddEditDevice.java:83)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at android.os.AsyncTask$2.call(AsyncTask.java:287)
04-04 21:24:08.351: E/AndroidRuntime(10745):    at java.util.concurrent.FutureTask.run(FutureTask.java:234)
04-04 21:24:08.351: E/AndroidRuntime(10745):    ... 4 more

来源：（更新了 SCF 的建议）

ADDEDITDEVICE.java

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.net.wifi.WifiInfo;
import android.net.wifi.WifiManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.ViewGroup;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.FrameLayout;
import android.widget.TextView;
import android.widget.TimePicker;
import java.text.DecimalFormat;


public class AddEditDevice extends Activity {

     private long rowID; 
     private EditText nameEt;
     private EditText capEt;
     private EditText codeEt;
     private TimePicker timeEt;
     private TextView ssidTextView;


      // @Override
       public void onCreate(Bundle savedInstanceState) 
       {
          super.onCreate(savedInstanceState); 
          setContentView(R.layout.add_country);
          WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
          WifiInfo info = wifi.getConnectionInfo();
          String ssidString = info.getSSID();

          //TextView ssidTextView = (TextView) findViewById(R.id.wifiSSID);
          ssidTextView = (TextView) findViewById(R.id.wifiSSID);
          ssidTextView.setText(ssidString); 

          nameEt = (EditText) findViewById(R.id.nameEdit);
          capEt = (EditText) findViewById(R.id.capEdit);
          codeEt = (EditText) findViewById(R.id.codeEdit);
          timeEt = (TimePicker) findViewById(R.id.timeEdit);






          Bundle extras = getIntent().getExtras(); 

          if (extras != null)
          {
             rowID = extras.getLong("row_id");
             nameEt.setText(extras.getString("name"));  
             capEt.setText(extras.getString("cap"));  
             codeEt.setText(extras.getString("code"));    
             String time = extras.getString("time");
             String[] parts = time.split(":");
             timeEt.setCurrentHour(Integer.valueOf(parts[0]));
             timeEt.setCurrentMinute(Integer.valueOf(parts[1]));
             timeEt.setIs24HourView(false);


          }

          Button saveButton =(Button) findViewById(R.id.saveBtn);
          saveButton.setOnClickListener(new OnClickListener() {

              public void onClick(View v) 
              {
                 if (capEt.getText().length() != 0)
                 {
                    AsyncTask<Object, Object, Object> saveContactTask = 
                       new AsyncTask<Object, Object, Object>() 
                       {
                          @Override
                          protected Object doInBackground(Object... params) 
                          {
                             saveContact();
                             return null;
                          }

                          @Override
                          protected void onPostExecute(Object result) 
                          {
                             finish();
                          }
                       }; 

                    saveContactTask.execute((Object[]) null); 
                 }

                 else
                 {
                    AlertDialog.Builder alert = new AlertDialog.Builder(AddEditDevice.this);
                    alert.setTitle(R.string.errorTitle); 
                    alert.setMessage(R.string.errorMessage);
                    alert.setPositiveButton(R.string.errorButton, null); 
                    alert.show();
                 }
              } 
         });}




           private void saveContact() 
           {
              DatabaseConnector dbConnector = new DatabaseConnector(this);

              if (getIntent().getExtras() == null)
              {
                  dbConnector.insertContact(nameEt.getText().toString(),
                          capEt.getText().toString(),
                          timeEt.getCurrentHour().toString() + ":"
                              + timeEt.getCurrentMinute().toString(),
                          codeEt.getText().toString(),
                       ssidTextView.getText().toString());

              }
              else
              {
                 dbConnector.updateContact(rowID,
                         nameEt.getText().toString(),
                            capEt.getText().toString(),
                              timeEt.getCurrentHour().toString() + ":"
                                  + timeEt.getCurrentMinute().toString(),
                              codeEt.getText().toString(),
                              ssidTextView.getText().toString());
              }
           }
}

来源：

数据库连接器.java

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;


public class DatabaseConnector {

    private static final String DB_NAME = "WorldCountries";
    private SQLiteDatabase database;
    private DatabaseOpenHelper dbOpenHelper;

    public DatabaseConnector(Context context) {
        dbOpenHelper = new DatabaseOpenHelper(context, DB_NAME, null, 1);
    }

       public void open() throws SQLException 
       {
          //open database in reading/writing mode
          database = dbOpenHelper.getWritableDatabase();
       } 

       public void close() 
       {
          if (database != null)
             database.close();
       }       

       public void insertContact(String name, String cap, String code, String time, String ssid) 
               {
                  ContentValues newCon = new ContentValues();
                  newCon.put("name", name);
                  newCon.put("cap", cap);
                  newCon.put("time", time);
                  newCon.put("code", code);
                  newCon.put("ssid", ssid);

                  open();
                  database.insert("country", null, newCon);
                  close();
               }


               public void updateContact(long id, String name, String cap, String code, String time, String ssid) 
               {
                  ContentValues editCon = new ContentValues();
                  editCon.put("name", name);
                  editCon.put("cap", cap);
                  editCon.put("time", time);
                  editCon.put("code", code);
                  editCon.put("ssid", ssid);

                  open();
                  database.update("country", editCon, "_id=" + id, null);
                  close();
               }


               public Cursor getAllContacts() 
               {
                  return database.query("country", new String[] {"_id", "name"}, 
                     null, null, null, null, "name");
               }

               public Cursor getOneContact(long id) 
               {
                  return database.query("country", null, "_id=" + id, null, null, null, null);
               }

               public void deleteContact(long id) 
               {
                  open(); 
                  database.delete("country", "_id=" + id, null);
                  close();
               }
}
4

1 回答 1

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我认为您的问题是您将 TextView 保存到局部变量“ssidTextView”中，而您应该将其保存到字段“ssid”中。只是改变

TextView ssidTextView = (TextView) findViewById(R.id.wifiSSID);

进入

ssid = (TextView) findViewById(R.id.wifiSSID);

当然，您还必须将“String ssid”重命名为其他名称，例如“ssidString”。

于 2013-04-05T00:12:28.557 回答