java - Android 从数据库获取数据到编辑 TextView 时遇到问题

Question

就像，如果我在编辑 TextView 中输入一些文本并按保存按钮，数据就会保存到数据库中。现在我希望，当我重新启动模拟器时，保存的文本将保留在编辑 TextView 中。我从数据库调用 getMsg() 方法来显示文本。 请看看我的代码...

MainActivity.java

public class MainActivity extends Activity implements LocationListener {
    String separator = "; ";
    private Button btn_cntct;
    private EditText message;
    LinearLayout linearLayoutSec;
    private Button GPSState;
    Button b_alert;
    Button b_save_message;
    public int REQUESTCODE = 1;
    int temp;
    ScrollView ScrView;
    Context c = MainActivity.this;
    Button AlertMessages;
    private static ArrayList<ContactItems> selectedContactList = new ArrayList<ContactItems>();
    static CustomAdapter adapter;
    public static String[] myvalue = new String[1];
    Spinner spinner;
    static String[] alert = { " ", "I am in danger", "Help Me", "Watch Out",
            "Look For Me", "Cover ME" };
    MySQLiteHelper dbHelper;
    String savedMessage;
    Button bsave;

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

                message = (EditText) findViewById(R.id.et_message);
        dbHelper = new MySQLiteHelper(this);
        String dis = dbHelper.getMsg();
        if (dis != null) {
            message.setText(dis);
        }

        bsave = (Button) findViewById(R.id.b_save);
        bsave.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                String str = message.getText().toString();
                dbHelper.updateMsg(str);

            }
        });

MySQLiteHelper.java

public class MySQLiteHelper extends SQLiteOpenHelper {

      public static final String TABLE_NAME = "userdetails";
      public static final String TABLE_NAME_MSG = "usermessage";
      public static final String COLUMN_ID = "_id";
      public static final String COLUMN_NUMBER = "NUMBER";
      public static final String COLUMN_NAME = "name";
      public static final String COLUMN_TYPE = "type";
      public static final String COLUMN_ID_MSG = "_id";
      public static final String COLUMN_MSG = "message";
      private static final String DATABASE_NAME = "userInformation.db";

      private static final int DATABASE_VERSION = 1;
      private static final String LOG = "DatabaseHelper";

      // Database creation sql statement
      private static final String DATABASE_CREATE_TABLE_CONTACTS = "create table "
          + TABLE_NAME + "(" + COLUMN_ID
          + " integer primary key autoincrement, " + COLUMN_NAME
          + " text not null,"+COLUMN_NUMBER+"  text not null,"+COLUMN_TYPE+" text not null);";
      private static final String DATABASE_CREATE_TABLE_MSG = "create table "
              + TABLE_NAME_MSG + "(" + COLUMN_ID_MSG
              + " integer primary key autoincrement, " + COLUMN_MSG    + " text not null);";
      private static final String DATABASE_INSERT_MSG = "insert into  "
              + TABLE_NAME_MSG + "(" + COLUMN_MSG+") VALUES('enter your message');";


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

      @Override
      public void onCreate(SQLiteDatabase database) {
        database.execSQL(DATABASE_CREATE_TABLE_CONTACTS);
        database.execSQL(DATABASE_CREATE_TABLE_MSG);
        database.execSQL(DATABASE_INSERT_MSG);

      }

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

      public long insertContact(ContactItems contItem) {
            SQLiteDatabase db = this.getWritableDatabase();

            ContentValues values = new ContentValues();
            values.put(COLUMN_NAME, contItem.getName());
            values.put(COLUMN_NUMBER, contItem.getNumber());
            values.put(COLUMN_TYPE, contItem.getType());

            // insert row
            long result = db.insert(TABLE_NAME, null, values);

            // assigning tags to todo
            /*for (long tag_id : tag_ids) {
                createTodoTag(todo_id, tag_id);
            }*/

            return result;
        }


      public ArrayList<ContactItems> getAllContacts() {
          ArrayList<ContactItems> contactList = new ArrayList<ContactItems>();
            String selectQuery = "SELECT  * FROM " + TABLE_NAME;

            Log.e(LOG, selectQuery);

            SQLiteDatabase db = this.getReadableDatabase();
            Cursor c = db.rawQuery(selectQuery, null);

            // looping through all rows and adding to list
            if (c.moveToFirst()) {
                do {
                    ContactItems conItems = new ContactItems();
                    conItems.setName(c.getString((c.getColumnIndex(COLUMN_NAME))));
                    conItems.setNumber((c.getString(c.getColumnIndex(COLUMN_NUMBER))));
                    conItems.setType(Integer.parseInt(c.getString(c.getColumnIndex(COLUMN_TYPE))));

                    // adding to todo list
                    contactList.add(conItems);
                } while (c.moveToNext());
            }

            return contactList;
        }

    public void updateMsg(String msg) {
        // TODO Auto-generated method stub
        // String selectQuery = "update  " + TABLE_NAME_MSG+" set "+COLUMN_MSG+" = '"+msg+"' where "+COLUMN_ID_MSG+" = 1";
          ContentValues values = new ContentValues();
            values.put(COLUMN_MSG, msg);
          SQLiteDatabase db = this.getReadableDatabase();
         db.update(TABLE_NAME_MSG, values, null, null);

    }
    public String getMsg() {
        String message ="";
          String selectQuery = "SELECT  * FROM " + TABLE_NAME_MSG;

          SQLiteDatabase db = this.getReadableDatabase();
            Cursor c = db.rawQuery(selectQuery, null);
            if (c.moveToFirst()) {
                do {
                    message = c.getString(c.getColumnIndex(COLUMN_MSG));
                } while (c.moveToNext());
            }

        // TODO Auto-generated method stub
            Log.e(LOG, "message = "+message);
        return message;

    }

    public int removeData(String number) {
        // TODO Auto-generated method stub

          SQLiteDatabase db = this.getReadableDatabase();
           //db.drawQuery(deleteQuery, null);
          return db.delete(TABLE_NAME, COLUMN_NUMBER + "='" + number+"'", null) ;

    }

    } 

Answer 1

我认为您的查询每次都会创建新表...

只需更改您的查询

private static final String DATABASE_CREATE_TABLE_CONTACTS = "create table if not exist "
          + TABLE_NAME + "(" + COLUMN_ID
          + " integer primary key autoincrement, " + COLUMN_NAME
          + " text not null,"+COLUMN_NUMBER+"  text not null,"+COLUMN_TYPE+" text not null);";
      private static final String DATABASE_CREATE_TABLE_MSG = "create table if not exist "
              + TABLE_NAME_MSG + "(" + COLUMN_ID_MSG
              + " integer primary key autoincrement, " + COLUMN_MSG    + " text not null);";

<小时/>

我建议你必须使用SharedPreferences而不是数据库。

检查下面的代码..

public class MainActivity extends Activity implements LocationListener {
    String separator = "; ";
    private Button btn_cntct;
    private EditText message;
    LinearLayout linearLayoutSec;
    private Button GPSState;
    Button b_alert;
    Button b_save_message;
    public int REQUESTCODE = 1;
    int temp;
    ScrollView ScrView;
    Context c = MainActivity.this;
    Button AlertMessages;
    private static ArrayList<ContactItems> selectedContactList = new ArrayList<ContactItems>();
    static CustomAdapter adapter;
    public static String[] myvalue = new String[1];
    Spinner spinner;
    static String[] alert = { " ", "I am in danger", "Help Me", "Watch Out",
            "Look For Me", "Cover ME" };
    MySQLiteHelper dbHelper;
    String savedMessage;
    Button bsave;

   -------------------------------------
   SharedPreferences sp; // edited
   -------------------------------------

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

         message = (EditText) findViewById(R.id.et_message);
   -------------------------------------
       sp=getSharedPreferences("user_data", Activity.MODE_PRIVATE); //Edited
       String saved_value=sp.getString("share_key","");
       message.setText(saved_value);
   -------------------------------------
        dbHelper = new MySQLiteHelper(this);
        //String dis = dbHelper.getMsg();
        //if (dis != null) {
        //    message.setText(dis);
       // }

        bsave = (Button) findViewById(R.id.b_save);
        bsave.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                String str = message.getText().toString();
                //dbHelper.updateMsg(str);
   -------------------------------------
              sp.edit().putString("str", str1).commit(); /Edited
   -------------------------------------
            }
        });