更新SQLite數據庫android

Question

好吧，我做了一個數據庫，我意識到，每次我改變數據庫中的東西我必須卸載，然後重新安裝應用程序:(這是非常令人沮喪的... 這裏是我的代碼爲我的數據基地希望你能幫助我，我不知道什麼是錯我的代碼：

import android.content.ContentValues; 
import android.content.Context; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 

public class Cook_tab_snacks_data extends SQLiteOpenHelper { 

public static final String DATABASE_NAME = "Snacks"; 

public Cook_tab_snacks_data(Context context) { 
    super(context, DATABASE_NAME, null, 1); 
} 

@Override 
public void onCreate(SQLiteDatabase db) { 

    String sql = "CREATE TABLE IF NOT EXISTS snacks (" + 
        "_id INTEGER PRIMARY KEY AUTOINCREMENT, " + 
        "name TEXT, " + 
        "disc TEXT, " + 
        "photo TEXT, " + 
        "prep TEXT, " + 
        "thumb TEXT, " + 
        "ingre TEXT, " + 
        "howto TEXT, " + 
        "info TEXT, " + 
        "snackId INTEGER)"; 
    db.execSQL(sql); 

    ContentValues values = new ContentValues(); 

    values.put("name", "Name 1"); 
    values.put("disc", "here is the description"); 
    values.put("photo", "stub.png"); 
    values.put("thumb", "stub.png"); 
    values.put("prep", "takes 30 mins"); 
    values.put("ingre", "the ingredients of the snack"); 
    values.put("howto", "how to make this thing"); 
    values.put("info", "basically its this much calorie and such and such"); 
    db.insert("snacks", "name", values); 

    values.put("name", "Name 2"); 
    values.put("disc", "here is the description"); 
    values.put("photo", "stub.png"); 
    values.put("thumb", "ic_launcher.png"); 
    values.put("prep", "takes 500 mins"); 
    values.put("ingre", "the ingredients of the snack"); 
    values.put("howto", "how to make this thing"); 
    values.put("info", "basically its this much calorie and such and such"); 
    db.insert("snacks", "name", values); 

    values.put("name", "Name 3"); 
    values.put("disc", "here is the description"); 
    values.put("photo", "stub.png"); 
    values.put("thumb", "stub.png"); 
    values.put("ingre", "the ingredients of the snack"); 
    values.put("howto", "how to make this thing"); 
    values.put("info", "basically its this much calorie and such and such"); 
    db.insert("snacks", "name", values); 

    values.put("name", "Name 4"); 
    values.put("disc", "here is the description"); 
    values.put("photo", "stub.png"); 
    values.put("ingre", "the ingredients of the snack"); 
    values.put("howto", "how to make this thing"); 
    values.put("info", "basically its this much calorie and such and such"); 
    db.insert("snacks", "name", values); 

    values.put("name", "Name 5"); 
    values.put("disc", "here is the description"); 
    values.put("photo", "stub.png"); 
    values.put("ingre", "the ingredients of the snack"); 
    values.put("howto", "how to make this thing"); 
    values.put("info", "basically its this much calorie and such and such"); 
    db.insert("snacks", "name", values); 

    values.put("name", "Name 6"); 
    values.put("disc", "here is the description"); 
    values.put("photo", "stub.png"); 
    values.put("ingre", "the ingredients of the snack"); 
    values.put("howto", "how to make this thing"); 
    values.put("info", "basically its this much calorie and such and such"); 
    db.insert("snacks", "name", values); 

    values.put("name", "Name 7"); 
    values.put("disc", "here is the description"); 
    values.put("photo", "stub.png"); 
    values.put("ingre", "the ingredients of the snack"); 
    values.put("howto", "how to make this thing"); 
    values.put("info", "basically its this much calorie and such and such"); 
    db.insert("snacks", "name", values); 

} 

@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    db.execSQL("DROP TABLE IF EXISTS snacks"); 
    onCreate(db); 
}} 

我似乎無法添加任何物品，或編輯任何項目，而無需反安裝應用程序然後再重新安裝:(請幫助！ !! 非常感謝！

Answer 1

不是卸載並重新安裝應用程序，只需增加數據庫的版本號碼呼叫onUpgrade方法。

public Cook_tab_snacks_data(Context context) { 
    super(context, DATABASE_NAME, null, 2); //previously 1, now 2 
} 

在你onUpgrade方法，首先它會刪除現有的表，然後將調用的onCreate方法重新

Answer 2

你也有，因爲數據庫只創建一次，如果你想要t o改變任何事情，你必須卸載它。

這是事物的工作方式

Answer 3

你onUpgrade功能是沒有得到所謂的，因爲表（S）數據庫的版本沒有變化。如果每次更改數據庫時增加版本號，onUpgrade函數都會將其刪除並重新創建。

最後輸入參數的超構造是數據庫的版本號：

public Cook_tab_snacks_data(Context context) { 
    super(context, DATABASE_NAME, null, 1); 
} 

Answer 4

的SQLiteOpenHelper的onCreate僅當創建數據庫調用。

如果你想要將其值添加到數據庫中，您可以在活動或服務通過實例化你的子類，調用getWritableDatabase()然後在你onCreate正在做同樣的方式調用insert這樣做。

如果你想改變模式，你需要在onUpgrade中這樣做。

notepad example是學習如何在應用中使用SQLiteDatabase的好地方，如果您需要一些練習。