如何从android java和sqlite中的数据库中检索值？ [英] How do I retrieve the value from database in android java and sqlite?

问题描述

你好，我是sqlite和android的新手。我正在尝试开发一个Android应用程序，我必须登录。我已经建立了一个数据库，但我没有确认它是否已连接并提供正确的查询输出或不是??????请帮帮我......我想在屏幕上看到表格的结果。

hello, I am new to sqlite and android. i m trying to develop an android app in which i have to do login. i had made a database but i am not confirmed that whether it is connected and giving the correct output of query or not?????? please help me..... i want to see the results of tables on the screen.

public class MainActivity extends Activity {

   private EditText  username=null;
   private EditText  password=null;
   private TextView attempts;
   private Button login;
   int counter = 3;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      username = (EditText)findViewById(R.id.editText1);
      password = (EditText)findViewById(R.id.editText2);
      attempts = (TextView)findViewById(R.id.textView5);
      attempts.setText(Integer.toString(counter));
      login = (Button)findViewById(R.id.button1);
   
   
   public void login(View view){
    String[][] userPass = { { "user1", "pass1" },
               { "user2", "pass2" },
               { "user3", "pass3" } };

String value1 = "userToCheck";
String value2 = "passToCheck";

boolean userOk = false;
for (String[] up : userPass)
if (value1.equals(up[0]) && value2.equals(up[1]))
userOk = true;

System.out.println("User authenticated: " + userOk);
Toast.makeText(getApplicationContext(), "Redirecting...", 
       Toast.LENGTH_SHORT).show();

   }
   public void onLocationChanged(Location loc) {       
 username.setText("");
       username.setVisibility(View.INVISIBLE);
       Toast.makeText(
               getBaseContext(),
               "Location changed : Lat: " + loc.getLatitude() + " Lng: "
                       + loc.getLongitude(), Toast.LENGTH_SHORT).show();
       String longitude = "Longitude: " + loc.getLongitude();
       String TAG = null;
 Log.v(TAG, longitude);
       String latitude = "Latitude: " + loc.getLatitude();
       Log.v(TAG, latitude);

       /*----------to get City-Name from coordinates ------------- */
       String cityName = null;
       Geocoder gcd = new Geocoder(getBaseContext(), Locale.getDefault());
       List<Address> addresses;
       try {
           addresses = gcd.getFromLocation(loc.getLatitude(),
                   loc.getLongitude(), 1);
           if (addresses.size() > 0)
               System.out.println(addresses.get(0).getLocality());
           cityName = addresses.get(0).getLocality();
       } catch (IOException e) {
           e.printStackTrace();
       }

       String s = longitude + "\n" + latitude + "\n\nMy Currrent City is: "
               + cityName;
       username.setText(s);
   }
   public void onProviderDisabled(String provider) {
       // TODO Auto-generated method stub
   }
   public void onProviderEnabled(String provider) {
       // TODO Auto-generated method stub
   }
   public void onStatusChanged(String provider, int status, Bundle extras) {
       // TODO Auto-generated method stub
   }
   @Override
   public boolean onCreateOptionsMenu(Menu menu) {
      // Inflate the menu; this adds items to the action bar if it is present.
      getMenuInflater().inflate(R.menu.main, menu);
      return true;
   }

}

public class DBOperations {

	// Database fields
	private static DataBaseWrapper dbHelper;
	private String[] User_TABLE_COLUMNS = { DataBaseWrapper.username,DataBaseWrapper.userid, DataBaseWrapper.password};
	private SQLiteDatabase database;
	private static DBOperations operations = null;

	private DBOperations()
	{
	}
	public DBOperations(Context context) {
		dbHelper = new DataBaseWrapper(context);
	}
	public void open() throws SQLException {
		database = dbHelper.getWritableDatabase();
	}
	public void close() {
		dbHelper.close();
	}
	public static DBOperations getInstance(Context context)
	  {
		  if(operations == null)
		  {
			  dbHelper = new DataBaseWrapper(context);			  
			  operations = new DBOperations();
		  }
		  return operations;
	  }

public UserClass adduser(String number, String string) {

		ContentValues values = new ContentValues();

		values.put(DataBaseWrapper.username, string);
		values.put(DataBaseWrapper.password, number);

		long userid = database.insert(DataBaseWrapper.User, null, values);

		// now that the user is registered return it ...
		Cursor cursor = database.query(DataBaseWrapper.User,
				User_TABLE_COLUMNS, DataBaseWrapper.userid + " = "
						+ userid, null, null, null, null);

		cursor.moveToFirst();

		UserClass newuser = parseUser(cursor);
		cursor.close();
		return newuser;
		
		
	}

public class DataBaseWrapper extends SQLiteOpenHelper {
//---------------------Table Users-------------------------
	public static final String User = "User";
	public static final String userid  = "userid";
	static final String username="username";
	static final String password="password";
	
	
	private static final String DATABASE_NAME = "fyp.db";
	protected static final int DATABASE_VERSION = 1;

private static final String UserCreate = "create table " + User
			+ "(" + userid + " integer primary key autoincrement, "
			+ username + " text not null);";
	
	
	public DataBaseWrapper(Context context) {
		super(context, DATABASE_NAME, null, DATABASE_VERSION);
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		db.execSQL(UserCreate);
		}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// you should do some logging in here
		// ..

		db.execSQL("DROP TABLE IF EXISTS "+User);

		onCreate(db);
	}
}

推荐答案

参考：在Android上使用SQLite数据库 [ ^ ]

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