Cómo almacenar JSON en SQLite

Question

Tengo problemas para almacenar datos JSON en sqlite. Este es el código que estoy tratando de implementar en este momento. Los datos JSON no son particularmente grandes, con solo 40 líneas.

La actividad principal es:

public class DatabaseActivity extends Activity { 
/** Called when the activity is first created. */ 

public DBAdapter 
DBAdapter =new DBAdapter(this); 

TextView txt; 
@Override 
public void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.main); 
// Create a crude view - this should really be set via the layout resources 
// but since its an example saves declaring them in the XML. 
LinearLayout rootLayout = new LinearLayout(getApplicationContext()); 
txt = new TextView(getApplicationContext()); 
rootLayout.addView(txt); 
setContentView(rootLayout); 

// Set the text and call the connect function. 
txt.setText("Connecting..."); 
//call the method to run the data retreival 
txt.setText(getServerData(KEY_13)); 

} 

public static final String KEY_13 = "http://xxx.xxx.xxx/api/train.php"; 


private String getServerData(String returnString) { 

InputStream is = null; 

String result = ""; 
//the train line to send 
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(); 
nameValuePairs.add(new BasicNameValuePair("code","A")); 

//http post 
try{ 
     HttpClient httpclient = new DefaultHttpClient(); 
     HttpPost httppost = new HttpPost(KEY_13); 
     httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs)); 
     HttpResponse response = httpclient.execute(httppost); 
     HttpEntity entity = response.getEntity(); 
     is = entity.getContent(); 

}catch(Exception e){ 
     Log.e("log_tag", "Error in http connection "+e.toString()); 
} 

//convert response to string 
try{ 
     BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8); 
     StringBuilder sb = new StringBuilder(); 
     String line = null; 
     while ((line = reader.readLine()) != null) { 
       sb.append(line + "\n"); 
     } 
     is.close(); 
     result=sb.toString(); 
}catch(Exception e){ 
     Log.e("log_tag", "Error converting result "+e.toString()); 
} 

//parse json data 
try{ 
     JSONArray jArray = new JSONArray(result); 
     for(int i=0;i<jArray.length();i++){ 
       JSONObject json_data = jArray.getJSONObject(i); 
       DBAdapter.insertTrain(json_data.getString("id"), 
            json_data.getString("code"), 
            json_data.getString("station"), 
            json_data.getString("platform"), 
            json_data.getString("timetillstation"), 
            json_data.getString("traindestination"), 

       //Get an output to the screen 
       returnString += "\n\t" + jArray.getJSONObject(i); 
     } 
}catch(JSONException e){ 
     Log.e("log_tag", "Error parsing data "+e.toString()); 
} 
return returnString; 
}  

} 

El adaptador es:

public class DBAdapter{ 
public static final String KEY_ID = "id"; 
public static final String KEY_Code = "code"; 
public static final String KEY_Station = "station"; 
public static final String KEY_Platform = "platform"; 
public static final String KEY_TimeTillStation = "timetillstation"; 
public static final String KEY_TrainDestination = "traindestination"; 
private static final String TAG = "DBAdapter"; 

private static final String DATABASE_NAME = "trains"; 
private static final String DATABASE_TABLE = "Mekerel"; 
private static final int DATABASE_VERSION = 1; 
private static final String DATABASE_CREATE = 
    "create table titles (id integer primary key, " 
    + "code text not null," 
    + "station text not null," 
    + "platform text not null," 
    + "timetillstation text not null," 
    + "traindestination text not null);"; 

private final Context context; 

private DatabaseHelper DBHelper; 
private SQLiteDatabase db; 
public DBAdapter(Context ctx) 
    { 
     this.context = ctx; 
     DBHelper = new DatabaseHelper(context); 
     this.db=DBHelper.getWritableDatabase(); 
    } 

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.w(TAG, "Upgrading database from version " + oldVersion 
       + " to " 
       + newVersion + ", which will destroy all old data"); 
     db.execSQL("DROP TABLE IF EXISTS titles"); 
     onCreate(db); 
    } 
}  

//---opens the database--- 
public DBAdapter open() throws SQLException 
{ 
    db = DBHelper.getWritableDatabase(); 
    return this; 
} 
//---closes the database---  
public void close() 
{ 
    DBHelper.close(); 
} 

//---insert a train into the database--- 
public long insertTrain(String id, String code, String station, String platform, String timetillstation, String traindestination) 
{ 
    ContentValues initialValues = new ContentValues(); 
    initialValues.put(KEY_ID, id); 
    initialValues.put(KEY_Code, code); 
    initialValues.put(KEY_Station, station); 
    initialValues.put(KEY_Platform, platform); 
    initialValues.put(KEY_TimeTillStation, timetillstation); 
    initialValues.put(KEY_TrainDestination, traindestination); 
    return db.insert(DATABASE_TABLE, null, initialValues); 
} 
//---retrieves all the ttrain--- 
public Cursor getAllTrains() 
{ 
    return db.query(DATABASE_TABLE, new String[] { 
      KEY_ID, 
      KEY_Code, 
      KEY_Station, 
      KEY_Platform, 
      KEY_TimeTillStation, 
      KEY_TrainDestination}, 
      null, 
      null, 
      null, 
      null, 
      null, 
      null); 
} 
//---retrieves a particular train--- 
public Cursor getTrain(long id) throws SQLException 
{ 
    Cursor mCursor = 
      db.query(true, DATABASE_TABLE, new String[] { 
      KEY_ID, 
      KEY_Code, 
      KEY_Station, 
      KEY_Platform, 
      KEY_TimeTillStation, 
      KEY_TrainDestination}, 
     KEY_ID + "=" + id, 
     null, 
     null, 
     null, 
     null, 
     null); 
    if (mCursor != null) { 
     mCursor.moveToFirst(); 
    } 
    return mCursor; 
} 
//---updates a train--- 
public boolean updateTrain(long id, String code, String station, String platform, String timetillstation, String traindestination) 
{ 
    ContentValues args = new ContentValues(); 
    args.put(KEY_Code, code); 
    args.put(KEY_Station, station); 
    args.put(KEY_Platform, platform); 
    args.put(KEY_TimeTillStation, timetillstation); 
    args.put(KEY_TrainDestination, traindestination); 
    return db.update(DATABASE_TABLE, args, 
        KEY_ID + "=" + id, null) > 0; 
} 
} 

No estoy seguro de dónde ir desde aquí ya que todavía hay problemas. El gato de registro muestra lo siguiente:

12-04 12:43:09.691: E/AndroidRuntime(21334): FATAL EXCEPTION: main 
12-04 12:43:09.691: E/AndroidRuntime(21334): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{ta.dabase/ta.dabase.DatabaseActivity}: java.lang.NullPointerException 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1680) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1784) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread.access$1500(ActivityThread.java:123) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:939) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.os.Handler.dispatchMessage(Handler.java:99) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.os.Looper.loop(Looper.java:130) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread.main(ActivityThread.java:3835) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at java.lang.reflect.Method.invokeNative(Native Method) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at java.lang.reflect.Method.invoke(Method.java:507) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at dalvik.system.NativeStart.main(Native Method) 
12-04 12:43:09.691: E/AndroidRuntime(21334): Caused by: java.lang.NullPointerException 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:118) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at ta.dabase.DBAdapter.<init>(DBAdapter.java:43) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at ta.dabase.DatabaseActivity.<init>(DatabaseActivity.java:32) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at java.lang.Class.newInstanceImpl(Native Method) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at java.lang.Class.newInstance(Class.java:1409) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 
12-04 12:43:09.691: E/AndroidRuntime(21334): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1672) 
12-04 12:43:09.691: E/AndroidRuntime(21334): ... 11 more 

Por último, me preguntaba si alguien me podría ayudar con la depuración en un sentido de qué y dónde colocar el código de registro adecuado para detectar de manera que el código va mal exactamente? Gracias

Answer 1

Para resolver este problema, debe seguir este pasos

1) crear la clase que contiene propiedades según sus datos JSON.

2) Deserialice sus datos json en su clase. (Cartografía de JSON con la clase)

3) almacenar los valores de todas las propiedades en esa clase en base de datos (SQLLite) (aplicación de clase con la base de datos)

4) **** ¡Guarde su trabajo ***!

¡Hecho! Disfruta Jsoning !!