从sqlite数据库中删除所有表

Question

我做了很多研究,无法找到合适的方法来删除SQLite数据库中的所有表.最后,我做了一个代码来从数据库中获取所有表名,我尝试逐个使用检索到的表名删除表.它没有用.

请建议我从数据库中删除所有表的方法.

这是我使用的代码:

public void deleteall(){
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor c = db.rawQuery("SELECT name FROM sqlite_master WHERE type='table'", null);
    do
    {
        db.delete(c.getString(0),null,null);
    }while (c.moveToNext());
}

deleteall()单击按钮时调用函数,代码如下:

public void ButtonClick(View view)
{
    String Button_text;
    Button_text = ((Button) view).getText().toString();

    if(Button_text.equals("Delete Database"))
    {
        DatabaseHelper a = new DatabaseHelper(this);
        a.deleteall();
        Toast.makeText(getApplicationContext(), "Database Deleted Succesfully!", Toast.LENGTH_SHORT).show();
    }}

Answer 1

用途DROP TABLE:

// query to obtain the names of all tables in your database
Cursor c = db.rawQuery("SELECT name FROM sqlite_master WHERE type='table'", null);
List<String> tables = new ArrayList<>();

// iterate over the result set, adding every table name to a list
while (c.moveToNext()) {
    tables.add(c.getString(0));
}

// call DROP TABLE on every table name
for (String table : tables) {
    String dropQuery = "DROP TABLE IF EXISTS " + table;
    db.execSQL(dropQuery);
}

Answer 2

Tim Biegeleisen 的回答几乎对我有用，但是因为我AUTOINCREMENT在我的表中使用了主键，所以有一个名为sqlite_sequence. 当例程试图删除该表时，SQLite 会崩溃。我也无法捕获异常。查看https://www.sqlite.org/fileformat.html#internal_schema_objects，我了解到可能有几个我不应该删除的内部架构表。文档说这些表中的任何一个都有以sqlite_开头的名称，所以我写了这个方法

private void dropAllUserTables(SQLiteDatabase db) {
    Cursor cursor = db.rawQuery("SELECT name FROM sqlite_master WHERE type='table'", null);
    //noinspection TryFinallyCanBeTryWithResources not available with API < 19
    try {
        List<String> tables = new ArrayList<>(cursor.getCount());

        while (cursor.moveToNext()) {
            tables.add(cursor.getString(0));
        }

        for (String table : tables) {
            if (table.startsWith("sqlite_")) {
                continue;
            }
            db.execSQL("DROP TABLE IF EXISTS " + table);
            Log.v(LOG_TAG, "Dropped table " + table);
        }
    } finally {
        cursor.close();
    }
}