更新 SQLite 数据库 android

Question

好的，我创建了一个数据库，我意识到每次我更改数据库中的某些内容时，我都必须卸载然后重新安装应用程序:(这非常令人沮丧... 这是我的数据库代码，希望你能帮助我！我不知道我的代码有什么问题：

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);
}}

我似乎无法添加任何项目，或编辑任何项目，而无需卸载应用程序然后重新安装:(请帮助！！！ 非常感谢！

Answer 1

无需再次卸载和安装应用程序，只需增加数据库的版本号即可调用 onUpgrade 方法。

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

与您的 onUpgrade 方法一样，它首先会删除现有表，然后调用 onCreate 方法重新创建表

Answer 2

您的 onUpgrade 函数没有被调用，因为数据库的版本没有改变。如果每次更改数据库时都增加版本号，onUpgrade 函数将删除它并重新创建它。

超级构造函数的最后一个输入参数是数据库版本号：

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

Answer 3

SQLiteOpenHelper 的onCreate 仅在创建数据库时调用。

如果您想向数据库添加值，您可以在 Activity 或 Service 中通过实例化您的子类来执行此操作，调用 getWritableDatabase()，然后调用 insert，就像在 onCreate 中所做的一样。

如果您想更改架构，您需要在 onUpgrade 中进行。

如果您需要一些练习，notepad example 是了解如何在应用中使用 SQLiteDatabase 的好地方。

Answer 4

你也有，因为数据库只创建一次，如果你想更改它的任何内容，你必须卸载它。

这就是事情的运作方式