android - 如何从 SQLite 数据库 Android Studio 中获取所有表

Question

我一直在寻找如何从数据库中获取所有表，我不熟悉 SQLite for Android Studio。我有一个 DBHelper 类，我用它来制作我的 sql 命令。到目前为止，我收集到的是我必须对 sqlite_master 进行查询，例如“ SELECT name FROM sqlite_master WHERE type='table' ”。
这是我的 DBHelper 类:

public class DBHelper extends SQLiteOpenHelper
{
public String tableName;
private static final String COLUMN_ID = "id";
private static final String COLUMN_NAME = "name";
private static final String COLUMN_DESC = "desc";
private static final String COLUMN_DECKNAME = "deckname";
private static final String COLUMN_IMAGENAME = "imagename";

public DBHelper(Context context, String tablename) {
    super(context, "UserDecks.db", null, 1);
    tableName = tablename;
}

public DBHelper(Context context){
    super(context, "UserDecks.db", null, 1);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE " + tableName + "(" + COLUMN_NAME + " TEXT, " + COLUMN_DESC + " TEXT, " + COLUMN_DECKNAME + " TEXT, " + COLUMN_IMAGENAME + " TEXT)");
}

@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1) {
    db.execSQL("DROP TABLE IF EXISTS " + tableName);
}

@Override
public void onOpen(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE IF NOT EXISTS " + tableName + "(" + COLUMN_NAME + " TEXT, " + COLUMN_DESC + " TEXT, " + COLUMN_DECKNAME + " TEXT, " + COLUMN_IMAGENAME + " TEXT)");
}

public Cursor GetDeckList(){
    SQLiteDatabase sdb = this.getReadableDatabase();
    Cursor cursor = sdb.rawQuery("SELECT name FROM sqlite_master WHERE type='table'", null);
    return cursor;
}

我只粘贴到 GetDeckList 方法的位置。
这是我引用 DBHelper 的地方:

    db = new DBHelper(this);
    Cursor cData = db.GetDeckList();
    int numOfRows = cData.getCount();
    if(numOfRows == 0){
        Toast.makeText(this, "Deck list is empty!", Toast.LENGTH_SHORT).show();
    }else{
        while(cData.moveToNext()){
            DL_deckList = new DeckList(cData.getString(0));
            LIST_currentDecks.add(DL_deckList);
        }
        mAdapter = new RecycleViewAdapter(true, LIST_currentDecks, this);
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        recyclerView.setAdapter(mAdapter);
        recyclerView.setHasFixedSize(false);
    }

我想我错过了一些代码，因为我正在做我在 stackoverflow 上阅读的关于如何从 sqlite_master 查询的内容，但是我的应用程序不断崩溃，因为我一直在尝试创建一个“空”表。当我修改代码时，它一直在调用“ onCreate ”或“ onOpen ”，即使我没有尝试制作表格。所以它一直在崩溃，因为我没有给它一个新表。所以我假设我错过了一些代码，但我不知道它是什么。

Answer 1

试试这样

db = new DBHelper(this);
Cursor cData = db.GetDeckList();
if(cData != null) {
    int numOfRows = cData.getCount();
    if(numOfRows == 0){
        Toast.makeText(this, "Deck list is empty!", Toast.LENGTH_SHORT).show();
    }else{
    
        List<String> tableNames = new ArrayList<String>();
        cData.moveToFirst();
        while (!cData.isAfterLast()) {
            tableNames.add(cData.getString(cData.getColumnIndex("name")));
            cData.moveToNext();
        }
        mAdapter = new RecycleViewAdapter(true, tableNames, this);
        
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        recyclerView.setAdapter(mAdapter);
        recyclerView.setHasFixedSize(false);
    }
}