NullPointerException在創建數據庫時

Question

我正在創建一個GPS跟蹤應用程序，我在開始階段，我使用LocationManager跟蹤了緯度和經度，現在我想要做的下一件事是將所有數據存儲在數據庫中，我有創建適配器類，並從MainActivity調用它，但在綁定上下文和打開數據庫時得到NullPointerException，請看看我的Logcat詳細信息，並請給我一個解決方案。

我越來越近

dbAdapter = new LocationDbAdapter(this); 
dbAdapter.open(); 

錯誤日誌中的錯誤消息：

android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:234) 
android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:149) 
om.example.androidtrackingapplication.LocationDbAdapter.open(LocationDbAdapter.java:78) 

我附上完整的logcat文件下面請讓我知道我錯了。

我將位置發送到適配器類，它將獲取值並存儲在表中。

我打電話給數據庫實例，當我得到的位置更新，當我點擊 定位按鈕，將調用LocationManager來獲取位置更新（這是我的應用程序崩潰點）。

LocationDbAdapter.java

  import android.content.ContentValues; 
      import android.content.Context; 
      import android.database.Cursor; 
      import android.database.SQLException; 
      import android.database.sqlite.SQLiteDatabase; 
      import android.database.sqlite.SQLiteOpenHelper; 
      import android.location.Location; 
      import android.util.Log; 

      public class LocationDbAdapter { 

       public static final String KEY_NAME = "name"; 
       public static final String KEY_LATITUDE = "latitude"; 
       public static final String KEY_LONGITUDE = "longitude"; 
       public static final String KEY_ACCURACY = "accuracy"; 
       public static final String KEY_TIME = "time"; 
       public static final String KEY_ROWID = "_id"; 

       private static final String TAG = "LocationDbAdapter"; 
       private DatabaseHelper mDbHelper; 
       private SQLiteDatabase mDb; 

       private static final String DATABASE_CREATE = 
        "create table locations (_id integer primary key autoincrement, " 
        + "name text not null, latitude real not null, longitude real not null, accuracy integer not null, time integer not null);"; 

       private static final String DATABASE_NAME = "data"; 
       private static final String DATABASE_TABLE = "locations"; 
       private static final int DATABASE_VERSION = 4; 

       private final Context mCtx; 

       private static class DatabaseHelper extends SQLiteOpenHelper { 

        DatabaseHelper(Context context) { 
         super(context, DATABASE_NAME, null, DATABASE_VERSION); 
        } 

        @Override 
        public void onCreate(SQLiteDatabase db) { 

         db.execSQL(DATABASE_CREATE); 
        } 

        @Override 
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
         Log.i(TAG, "Upgrading database from version " + oldVersion + " to " 
           + newVersion + ", which will destroy all old data"); 
         db.execSQL("DROP TABLE IF EXISTS locations"); 
         onCreate(db); 
        } 
       } 

       /** 
       * Constructor - takes the context to allow the database to be 
       * opened/created 
       * 
       * @param ctx the Context within which to work 
       */ 
       public LocationDbAdapter(Context ctx) { 
        this.mCtx = ctx; 

       } 

       /** 
       * Open the notes database. If it cannot be opened, try to create a new 
       * instance of the database. If it cannot be created, throw an exception to 
       * signal the failure 
       * 
       * @return this (self reference, allowing this to be chained in an 
       *   initialization call) 
       * @throws SQLException if the database could be neither opened or created 
       */ 
       public LocationDbAdapter open() throws SQLException { 
        mDbHelper = new DatabaseHelper(mCtx); 
        mDb = mDbHelper.getWritableDatabase(); 
        return this; 
       } 

       public void close() { 
        mDbHelper.close(); 
       } 


       /** 
       * Add new location. If the location is 
       * successfully created return the new rowId, otherwise return 
       * a -1 to indicate failure. 
       * 
       * @param location 
       * @return rowId or -1 if failed 
       */ 
       public long addLocation(Location location) { 
        Log.i(TAG, "Writing new location:"+location.toString()); 
        ContentValues contentValues = new ContentValues(); 
        contentValues.put(KEY_NAME, location.getProvider()); 
        contentValues.put(KEY_LATITUDE, location.getLatitude()); 
        contentValues.put(KEY_LONGITUDE, location.getLongitude()); 
        contentValues.put(KEY_ACCURACY, location.getAccuracy()); 
        contentValues.put(KEY_TIME, location.getTime()); 

        return mDb.insert(DATABASE_TABLE, null, contentValues); 
       } 

       public int clearDatabase() { 
        Log.i(TAG, "clearDatabase()"); 
        return mDb.delete(DATABASE_TABLE, null, null); 
       } 

       public Cursor fetchAllLocations() { 

        return mDb.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NAME, KEY_LATITUDE, KEY_LONGITUDE, KEY_ACCURACY, 
          KEY_TIME}, null, null, null, null, null); 
       } 
      } 

MainActivity.java

 package com.example.androidtrackingapplication; 

     import java.io.BufferedReader; 
     import java.io.IOException; 
     import java.io.InputStream; 
     import java.io.InputStreamReader; 
     import java.util.Timer; 
     import java.util.TimerTask; 

     import org.apache.http.HttpResponse; 
     import org.apache.http.client.HttpClient; 
     import org.apache.http.client.methods.HttpPost; 
     import org.apache.http.impl.client.DefaultHttpClient; 



     import android.app.Activity; 
     import android.app.Service; 
     import android.content.Context; 
     import android.content.Intent; 
     import android.content.IntentFilter; 
     import android.location.GpsStatus; 
     import android.location.Location; 
     import android.location.LocationListener; 
     import android.location.LocationManager; 
     import android.location.LocationProvider; 
     import android.os.BatteryManager; 
     import android.os.Bundle; 
     import android.os.CountDownTimer; 
     import android.os.IBinder; 
     import android.util.Log; 
     import android.view.View; 
     import android.widget.Button; 
     import android.widget.EditText; 
     import android.widget.Toast; 


     public class MainActivity extends Activity 

     { 
      LocationManager mlocManager ; 
      LocationListener mlocListener ; 
       Location loc; 
      double lat; 
      double longitude; 
      EditText Lat; 
      EditText Long,battery,hitTime,intervalTime; 
      int level = -1; 
      static int i; 
      Button Send,Reset,Locate,Close;  

      private LocationDbAdapter dbAdapter; 
      Timer t; 
      protected CountDownTimer waitTimer; 

     /** Called when the activity is first created. */ 

     @Override 

     public void onCreate(Bundle savedInstanceState) 

     { 

     super.onCreate(savedInstanceState); 

     setContentView(R.layout.activity_main); 

     Lat= (EditText) findViewById(R.id.editText1); 
     Long=(EditText) findViewById(R.id.editText2); 


     //hitTime= (EditText) findViewById(R.id.editText3); 
     //intervalTime=(EditText) findViewById(R.id.editText4); 

     Locate=(Button) findViewById(R.id.button1); 
     Send= (Button) findViewById(R.id.button2); 

     Close=(Button) findViewById(R.id.button3); 




     Locate.setOnClickListener(new View.OnClickListener() { 
      public void onClick(View v) { 

      // String hit=hitTime.getText().toString(); 
       // int hit1= Integer.parseInt(hit); 
       // System.out.println("Hit"+hit1); 


       Send.setEnabled(false); 
        Lat.setText(" "); 
        Long.setText(" "); 

      /* Enable the Gps */ 

        Intent intent = new Intent("android.location.GPS_ENABLED_CHANGE"); 
       intent.putExtra("enabled", true); 
       sendBroadcast(intent); 

        waitTimer = new CountDownTimer(60000,1000) { 

          public void onTick(long millisUntilFinished) { 
           i = i+1; 
           System.out.println("IN:"+i); 


            mlocManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE); 
            mlocListener = new MyLocationListener(); 
          loc = mlocManager.getLastKnownLocation(LocationManager.GPS_PROVIDER); 

          //  mlocManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,300000, 0, mlocListener); 
          //mlocManager.requestSingleUpdate(LocationManager.GPS_PROVIDER,mlocListener, null); 

          mlocManager.requestSingleUpdate(LocationManager.GPS_PROVIDER,mlocListener, null); 
          } 

          public void onFinish() { 
          System.out.println("Location not found"); 
         Toast.makeText(getApplicationContext(), "Location Not Found ", Toast.LENGTH_LONG).show(); 

         if(mlocManager!=null) 
         { 

         } 
          Lat.setText(" "); 
         Long.setText(" "); 


         if(loc!=null) 
         { 
          Lat.setText(String.valueOf(loc.getLatitude())); 
          Long.setText(String.valueOf(loc.getLongitude())); 
         } 
         Toast.makeText(getApplicationContext(), "Last Location ",Toast.LENGTH_LONG).show(); 



        Intent intent = new Intent("android.location.GPS_ENABLED_CHANGE"); 
         intent.putExtra("enabled", false); 
         sendBroadcast(intent); 

          } 
         }.start(); 

      } 
     }); 






     Send.setOnClickListener(new View.OnClickListener() { 
      public void onClick(View v) { 





      // String lat1="15."; 
      // String longitude1="75."; 
      HttpClient httpClient = new DefaultHttpClient(); 

      String postURL = ""; 

      postURL = "http://bb.trackfleet.biz/android_gps/lat_long.php?lat="+lat+"&long="+longitude; 


      HttpPost httpPost = new HttpPost(postURL); 

      HttpResponse httpResponse = null; 

      try 
      { 
       Toast.makeText(getApplicationContext(),"send", Toast.LENGTH_SHORT).show(); 
       httpResponse = httpClient.execute(httpPost); 

       String str = inputStreamToString(httpResponse.getEntity().getContent()).toString(); 

       Toast.makeText(getApplicationContext(), str, Toast.LENGTH_SHORT).show(); 
      } 
      catch(Exception ex) 
      { 
       Toast.makeText(getApplicationContext(),"error", Toast.LENGTH_SHORT).show(); 

      } 

      } 
     }); 


     Close.setOnClickListener(new View.OnClickListener() { 
      public void onClick(View v) { 


       if(mlocManager!=null) 
       { 
        mlocManager.removeUpdates(mlocListener); 
        mlocManager=null; 
       } 

       Intent intent = new Intent("android.location.GPS_ENABLED_CHANGE"); 
        intent.putExtra("enabled", false); 
        sendBroadcast(intent); 

     finish(); 



      } 
     }); 




     } 






     private StringBuilder inputStreamToString(InputStream is) { 
      String line = ""; 
      StringBuilder total = new StringBuilder(); 
      // Wrap a BufferedReader around the InputStream 
      BufferedReader rd = new BufferedReader(new InputStreamReader(is)); 
      // Read response until the end 
      try { 
       while ((line = rd.readLine()) != null) { 
        total.append(line); 
       } 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 
      // Return full string 
      return total; 
     } 

MyLocationListener服務

 public class MyLocationListener extends Service implements LocationListener 

     { 

      @Override 
      public void onCreate() { 

       dbAdapter = new LocationDbAdapter(this); 
       dbAdapter.open(); 
      } 




     @Override 

     public void onLocationChanged(Location loc) 

     { 

     if(loc!=null) 
     { 
      dbAdapter = new LocationDbAdapter(this); 
      dbAdapter.open(); 
      long id=dbAdapter.addLocation(loc); 
      Toast.makeText(getApplicationContext(), "Added Data Sucessfully " +id ,Toast.LENGTH_SHORT).show(); 
     } 
     lat=loc.getLatitude(); 

     longitude=loc.getLongitude(); 

      waitTimer.cancel(); 
     String Text = "My current location is: " + 

     "Latitud = " + loc.getLatitude() + 

     "Longitud = " + loc.getLongitude(); 


     Lat.setText(String.valueOf(lat)); 
     Long.setText(String.valueOf(longitude)); 


     if((Lat.getText()!=null) && (Long.getText()!=null)) 
     { 
       Send.setEnabled(true); 


       Send.performClick(); 


     } 



     } 


     @Override 

     public void onProviderDisabled(String provider) 

     { 

     Toast.makeText(getApplicationContext(),"Gps Disabled Pls Enable It",Toast.LENGTH_SHORT).show(); 
     startActivity(new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS)); 

     } 


     @Override 

     public void onProviderEnabled(String provider) 

     { 

     Toast.makeText(getApplicationContext(),"Gps Enabled",Toast.LENGTH_SHORT).show(); 

     } 


     @Override 

     public void onStatusChanged(String provider, int status, Bundle extras) 

     { 

     } 

     @Override 
     public void onDestroy() 
     { 

      super.onDestroy(); 
      dbAdapter.close(); 
      mlocManager.removeUpdates(this); 
     } 
     @Override 
     public IBinder onBind(Intent intent) { 
      // TODO Auto-generated method stub 
      return null; 
     } 
     } 
     } 

Answer 1

如果你問我，你的模式是不正確的源碼，如果「自動增量」的SQLite是你需要，你必須使用的功能：

id INTEGER PRIMARY KEY 

，你有沒有不應該在那裏的自動增量。

或者自動增量不起作用。請參閱create文檔

順便說一下，如果您使用INTEGERS保存座標而不是float/double等，可以加快您的應用程序的速度。請查看this answer of mine解釋如何輕鬆使用整數。能夠使用整數是非常有用的。 （索引，memcache鍵等）

更新：測試sqlite2/3。在sqlite3上運行，但不在sqlite2上運行：

SQL error: near "autoincrement": syntax error 

因此，如果目標是sqlite3，那麼您應該去。