[英]Create database in Android splash-screen
我的應用程序中有一個初始屏幕,試圖檢查數據庫表是否存在,如果不存在,請創建應用程序所需的表。 我的想法是進行2次檢查,如下所示:
if(db.exists){
increase the progressbar to the 100%
(If we could add a short pause to the progress bar transition better, just
for a better user experience)}
else{
increase the progress bar to 50% and create databases. By last increase
progress bar to 100%}
start -> main_activity
這只是我的想法,但我不知道如何制作和引用AppSQLiteHelper.java的方法。 如果您有更好的想法可以更好地改進代碼邏輯。 這是到目前為止編寫的代碼:
SplashScreenActivity.java:
public class SplashScreenActivity extends Activity {
// Set the duration of the splash screen
public ProgressBar splash_screenProgressBar;
public int MAX_VALUE = 30;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Set portrait orientation
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
setContentView(R.layout.splash_screen);
splash_screenProgressBar = (ProgressBar) findViewById(R.id.splash_screenProgressBar);
splash_screenProgressBar.setMax(MAX_VALUE);
new CountDownTimer(3000, 100) {
int progreso = 1; // Variable que va a ir aumentando del progreso
@Override
public void onTick(long millisUntilFinished) {
splash_screenProgressBar.setProgress(progreso);
progreso += (1);
}
@Override
public void onFinish() {
splash_screenProgressBar.setProgress(MAX_VALUE);
// Start the next activity
Intent mainIntent = new Intent().setClass(SplashScreenActivity.this, MainActivity.class);
startActivity(mainIntent);
// Close the activity so the user won't able to go back this activity pressing Back button
finish();
}
}.start();
}
}
AppSQLiteHelper.java:
public class AppSQLiteHelper extends SQLiteOpenHelper{
String sqlCreateCartera = "CREATE TABLE CARTERA (saldo INTEGER)";
String sqlCreateValor = "CREATE TABLE VALOR (cantidad INTEGER, precio_accion INTEGER, entidad TEXT)";
String sqlCreateEstado = "CREATE TABLE ESTADO (estado BOOLEAN)";
public AppSQLiteHelper(Context contexto, String nombre,
CursorFactory factory, int version) {
super(contexto, nombre, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(sqlCreateCartera);
db.execSQL(sqlCreateValor);
db.execSQL(sqlCreateEstado);
}
@Override
public void onUpgrade(SQLiteDatabase db, int versionAnterior, int versionNueva) {
db.execSQL("DROP TABLE IF EXISTS CARTERA");
db.execSQL("DROP TABLE IF EXISTS VALOR");
db.execSQL("DROP TABLE IF EXISTS ESTADO");
db.execSQL(sqlCreateCartera);
db.execSQL(sqlCreateValor);
db.execSQL(sqlCreateEstado);
}
}
為什么要檢查數據庫是否存在,因為一旦創建AppSQLiteHelper
對象,它就會自動調用onCreate()
的重寫函數來初始化數據庫,而不必顯式檢查數據庫是否存在。如果確實有上述條件,您仍然確實想這樣做,那么您可以創建一個回調接口並在您的幫助器類中實現,在oncreate執行之后,您可以檢查其是否在下面創建了db.Like。
public interface OnDBInitializeListener {
public void onCreateCalled(int position);
}
並在將其傳遞給構造函數時調用幫助程序類時使用此方法。希望有幫助
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