Java 在Android中创建数据库

好的，我已经学习了一些教程，在学习了一个教程之后创建了一个databaseHelper类。然而，我不完全理解或者不知道如何实际创建数据库

在我的mainActivity中，我已经将其添加到onCreate中，但它不会创建任何数据库，或者至少在我的Android设备监视器中没有显示任何内容

基本上，我应该如何创建数据库

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

    sharedPreferences = getSharedPreferences(PREFERENCES, Context.MODE_PRIVATE);

    dbHelper = new databaseHelper(this);

}

爪哇

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非常感谢您的帮助。

如android文档中所述，在调用getWritableDatabase或getReadableDatabase之一之前，不会实际创建或打开数据库

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链接：

看看这个我以前试过，但没用。然而，我刚刚意识到我是个白痴。我没有为最后3个表分配主键，因此应用程序只是抛出了一个错误。您的答案成功，因此您被选中。

public class databaseHelper extends SQLiteOpenHelper {

static final String DATABASEHELPER = "DATABASE HELPER";

static final String dbName="chefs";

//User Table Fields
static final String userTable="user";
static final String userColID="userID";
static final String userColName="firstName";
static final String userColLast="lastName";
static final String userColDOB="DOB";
static final String userColGend="gender";
static final String userColAddr="address";
static final String userColPost="postcode";
static final String userColBio="bio";
static final String userColUser="username";
static final String userColEmail="email";
static final String userColPass="password";
static final String userColPic="picture";
static final String userColLastLog="lastlogin";
static final String userColLastLogIP="lastloginIP";
static final String userColRegisteredIP="registeredIP";
static final String userColCreatedOn="createdOn";

//Recipe Table Fields
static final String recipeTable="recipe";
static final String recipeColID="recipeID";
static final String recipeColName="name";
static final String recipeColCate="category";
static final String recipeColDesc="description";
static final String recipeColUserID="user_userID";

//Ingredient Table Fields
static final String ingredientTable="ingredient";
static final String ingredientColID="ingredientID";
static final String ingredientColRecipeID="recipe_recipeID";
static final String ingredientColName="name";
static final String ingredientColAmount="amount";
static final String ingredientColUnit="unit";

//Step Table Fields
static final String stepTable="step";
static final String stepColID="stepID";
static final String stepColRecipeID="recipe_recipeID";
static final String stepColNumber="stepNumber";
static final String stepColDesc="description";

public databaseHelper(Context context) {
    super(context, dbName, null,1);

    Log.d(DATABASEHELPER, "Database Created");
}

@Override
public void onCreate(SQLiteDatabase db) {

    // Creating User Table
    db.execSQL("CREATE TABLE "+userTable+" ("+userColID+" INTEGER PRIMARY KEY AUTOINCREMENT, "+userColName+" TEXT, "+userColLast+" TEXT, "
            +userColDOB+" NUMERIC, "+userColGend+" TEXT, "+userColAddr+" TEXT, "+userColPost+" TEXT, "+userColBio+" TEXT, "
            +userColUser+" TEXT, "+userColEmail+" TEXT, "+userColPass+" TEXT, "+userColPic+" TEXT, "+userColLastLog+" NUMERIC, "
            +userColLastLogIP+" TEXT, "+userColRegisteredIP+" TEXT, "+userColCreatedOn+" NUMERIC)");

    // Creating Recipe Table
    db.execSQL("CREATE TABLE "+recipeTable+" ("+recipeColID+" INTEGER AUTOINCREMENT, "+recipeColName+" INTEGER, "+recipeColCate+" TEXT, "
            +recipeColDesc+" TEXT, "+recipeColUserID+" INTEGER");

    // Creating Ingredient Table
    db.execSQL("CREATE TABLE "+ingredientTable+" ("+ingredientColID+" INTEGER AUTOINCREMENT, "+ingredientColRecipeID+" TEXT ,"+ingredientColName+" TEXT, "
            +ingredientColAmount+" INTEGER, "+ingredientColUnit+" TEXT");

    db.execSQL("CREATE TABLE "+stepTable+" ("+stepColID+" INTEGER AUTOINCREMENT, "+stepColRecipeID+" INTEGER, "+stepColNumber+" INTEGER, "
            +stepColDesc+" TEXT");


}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    Log.d(DATABASEHELPER, "Upgrading Database");

}
}