我是开发Android应用程序的新手，我想在导航抽屉中成功登录后显示用户名。我的问题是如何从sqlite数据库中只获取用户名并在textView中显示它。 See the picture
这是我的代码到目前为止，我的DatabaseHelper
public class DatabaseHelper extends SQLiteOpenHelper{
public static final String DATABASE_NAME = "Users.db";
public static final String TABLE_NAME = "users_table";
private static final int DATABASE_VERSION = 1;
private static final String KEY_ID = "id";
private static final String KEY_NAME = "username";
private static final String KEY_PASS = "password";
SQLiteDatabase db;
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE "+TABLE_NAME+" (_id INTEGER PRIMARY KEY AUTOINCREMENT, username TEXT, password TEXT);");
db.execSQL("INSERT INTO " + TABLE_NAME + " VALUES (null, 'admin', '12345');");
}
public String searchPass(String uname){
db = this.getReadableDatabase();
String query = "SELECT username, password FROM "+TABLE_NAME;
Cursor cursor = db.rawQuery(query, null);
String a, b;
b = "not found";
if(cursor.moveToFirst()){
do{
a = cursor.getString(0);
if(a.equals(uname)){
b = cursor.getString(1);
break;
}
}while(cursor.moveToNext());
}
return b;
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
} }
这是我要显示我的用户名
的地方public class MenuHome extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
public static final String PREFS_NAME = "LoginPrefs";
DatabaseHelper helper = new DatabaseHelper(this);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_menu_home);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
//set the fragment initially
HomeFragment fragment = new HomeFragment();
setTitle(R.string.ttl_home);
FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
/*@Override //Right Options Menu
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_home, menu);
return true;
}*/
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return false;
}
return super.onOptionsItemSelected(item);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_home) {
HomeFragment fragment = new HomeFragment();
setTitle(R.string.ttl_home);
android.support.v4.app.FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
} else if (id == R.id.nav_inv) {
InventoryFragment fragment = new InventoryFragment();
setTitle(R.string.ttl_inventory);
android.support.v4.app.FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
} else if (id == R.id.nav_prod) {
ProductFragment fragment = new ProductFragment();
setTitle(R.string.ttl_products);
android.support.v4.app.FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
} else if (id == R.id.nav_clients) {
ClientsFragment fragment = new ClientsFragment();
setTitle(R.string.ttl_clients);
android.support.v4.app.FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
} else if (id == R.id.nav_stat) {
StatsFragment fragment = new StatsFragment();
setTitle(R.string.ttl_stat);
android.support.v4.app.FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
} else if (id == R.id.nav_prof) {
ProfileFragment fragment = new ProfileFragment();
setTitle(R.string.ttl_prof);
android.support.v4.app.FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
} else if (id == R.id.nav_about) {
AboutFragment fragment = new AboutFragment();
setTitle(R.string.ttl_about);
android.support.v4.app.FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
} else if (id == R.id.nav_logout) {
SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
SharedPreferences.Editor editor = settings.edit();
editor.remove("logged");
editor.commit();
Intent intent = new Intent(MenuHome.this, MainActivity.class);
startActivity(intent);
finish();
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
} }
答案 0 :(得分：0)
我会将用户名保存到sharedpreferences，因为app只有一个用户，您不需要只保存一个条目到数据库。但是如果你坚持从数据库中获取它，那么将此函数添加到DatabaseHelper。
public String getUsername() throws SQLException {
String username = "";
Cursor cursor = this.getReadableDatabase().query(
TABLE_NAME, new String[] { KEY_NAME },
null, null, null, null, null);
if (cursor.moveToFirst()) {
do {
username = cursor.getString(0);
} while (cursor.moveToNext());
}
cursor.close();
return username;
}
以后您可以使用此代码在抽屉活动中获取用户名：
textView.setText(helper.getUsername());
P.S。你真的应该重构你的代码。并使用SharedPreferences而不是SQLite来存储单个值。 SQLite旨在存储海量数据容器，如缓存列表数据等。