Java - Android Studio - 數據庫返回列名稱，而不是列中的消息

Question

有一個奇怪的問題我花了一些時間在我輸入消息到聊天應用程序的位置。消息進入arrayList以及數據庫。當我離開應用程序的聊天部分時，我希望能夠返回並將數據庫中現有的消息插入到arrayList中，以便它們可見。

當我重新進入應用程序的聊天部分時，我得到的只是「KEY_MESSAGE」而不是實際輸入的消息。

任何想法？

感謝

public class ChatWindow extends AppCompatActivity { 

ListView listView; 
Button sendButton; 
ArrayList<String> arrayList = new ArrayList<String>(); // arrayList to hold "chat" 
ChatDatabaseHelper Cdb; 


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


    listView = (ListView)findViewById(R.id.chatListView); 
    final EditText editText = (EditText)findViewById(R.id.messageText); 
    sendButton = (Button)findViewById(R.id.sendButton); 
    final ChatAdapter messageAdapter = new ChatAdapter(this); 
    listView.setAdapter(messageAdapter); 
    Cdb = new ChatDatabaseHelper(this); 

    Cursor cursor = Cdb.getMessages(); 

    while (cursor.moveToNext()) { 

     arrayList.add(cursor.getString(cursor.getColumnIndex(Cdb.KEY_MESSAGE))); 
    } 


    sendButton.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 

       String chatText = editText.getText().toString(); // changing editText to String 
       arrayList.add(chatText); // adding the string from EditTest to arrayList 

       boolean isInserted = Cdb.insertData(chatText); // inserting the message text into the database 
       if(isInserted = true) 
        Toast.makeText(ChatWindow.this,"Message Sent",Toast.LENGTH_SHORT).show(); 
       else 
        Toast.makeText(ChatWindow.this,"Message not Sent",Toast.LENGTH_SHORT).show(); 
       messageAdapter.notifyDataSetChanged(); 
       editText.setText(" "); 

      } 

     }); 




} 
// for loop class. 
class ChatAdapter extends ArrayAdapter<String>{ // custom adapter class // when youc all the adapter it forms the for loop for you. 

    public ChatAdapter(Context ctx) { 
     super(ctx, 0); 
    } // default constructor 

    // method to return the number of rows that will be in your array 
    public int getCount(){ // will tell how many times to run a for loop 

     return arrayList.size(); //will return the size of the array 
    } 

    public String getItem(int position){ 

     return arrayList.get(position); // will return the item at position 
    } 

    // getview method 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     LayoutInflater Inflater = ChatWindow.this.getLayoutInflater(); // an inflater inflates the xml layout into a view. 
     View result = null; 
     if(position%2 == 0){ // if position number in the array is odd do this, if number is even, do this. 
      result = Inflater.inflate(R.layout.chat_row_incoming, null); // depending on the position, show layout incoming 

     } else { 
      result = Inflater.inflate(R.layout.chat_row_outgoing,null); // depending on the position, show layout outgoing 

     } 

     TextView message = (TextView)result.findViewById(R.id.messageText); // creating a message of type TextView connected to messageText 
     message.setText(getItem(position));         // the messageText is the input typed in. 

     return result; // return the view which is the Inflater. 


    } 
} // end of chat adapter class 

@Override 
protected void onDestroy(){ 
    super.onDestroy(); 
    Cdb.close(); 
    String ACTIVITY_NAME = "ChatWindow"; 
    Log.i(ACTIVITY_NAME,"In onDestroy()"); 
} 



} 

這是我的數據庫幫助類：

public class ChatDatabaseHelper extends SQLiteOpenHelper { 

public static final String DATABASE_NAME = "Chats.db"; 
public static final String TABLE_NAME = "chatMessages"; 
public static final int dbVersion = 1; 
public static final int KEY_ID = 0; 
public static final String KEY_MESSAGE = "MESSAGE"; 


public ChatDatabaseHelper(Context context) { 
    super(context, DATABASE_NAME, null, dbVersion); 

} 

@Override 
public void onCreate(SQLiteDatabase db) { 

    db.execSQL("create table " +TABLE_NAME+ "(ID INTEGER PRIMARY KEY AUTOINCREMENT,"+KEY_MESSAGE+" text)"); 
    Log.i("ChatDataBaseHelper","Calling OnCreate"); 


} 

@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME); 
    onCreate(db); 
    Log.i("ChatDataBaseHelper","Calling OnUpgrade, oldVersion=" + oldVersion + "newVersion" + newVersion); 
} 

public boolean insertData(String message){ 
    SQLiteDatabase db = this.getWritableDatabase(); // creating the database 
    ContentValues contentValues = new ContentValues(); 

    try { 

     contentValues.put(KEY_MESSAGE, message); 
     db.insert(TABLE_NAME, null, contentValues); 

     return true; 
    }catch(Exception e){ 
     return false; 
    } 
} 



public Cursor getMessages(){ 
    SQLiteDatabase db = this.getWritableDatabase(); // creating the database 
    Cursor msg = db.rawQuery("select * from " + TABLE_NAME,null); 

    return msg; 

    } 
} 

Answer 1

相反Cursor msg = db.rawQuery("select * from " + TABLE_NAME,null)，你必須使用類似的東西壽這樣的：

public String createDBandReturnValue(){ 
    SQLiteDatabase banco = context.openOrCreateDatabase("DATABASE_NAME", DATABASE_ACESS, null);//DATABASE_ACESS=0,1 or 2 
    Cursor cursor = banco.query("TABLE_NAME", null, null, null, null, null, null); 
    String str = cursor.getString(cursor.getColumnIndex("COLUMN_NAME_YOU_WANT_TO_RETURN")); 
} 

記得關德連接後。這snipet這一切你需要...