Question

每次停止应用程序时，都不会显示数据库中的数据，而是从第一个数据库创建数据库。我不确切地知道问题出在哪里需要更多准确的指导现在存储和显示信息，但是当从最近的应用程序关闭应用程序时，将重建数据库。

public SevenLearnDatabaseOpenHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    this.context = context;
}

@Override
public void onCreate(SQLiteDatabase db) {
    try {

        db.execSQL("CREATE TABLE IF NOT EXISTS " + POST_TABLE_NAME + " (" +
                COL_ID + " INTEGER PRIMARY KEY, " +
                COL_PAGE + " TEXT, " +
                COL_PAGE2 + " TEXT, " +
                COL_NIAT + " TEXT, " +
                COL_DATE + " TEXT);");

        Log.e(TAG, "onCreate: " + "create database");

    } catch (SQLException e) {
        Log.e(TAG, "onCreate: " + e.toString());
    }
}

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

}


public boolean addPost(Post post) {
    ContentValues cv = new ContentValues();
    cv.put(COL_ID, post.getId());
    cv.put(COL_PAGE, post.getPage());
    cv.put(COL_PAGE2, post.getPage2());
    cv.put(COL_NIAT, post.getNiat());
    cv.put(COL_DATE, post.getDate());

    SQLiteDatabase sqLiteDatabase = this.getWritableDatabase();
    long isInserted = sqLiteDatabase.insert(POST_TABLE_NAME, null, cv);

    Log.i(TAG, "addPost: " + isInserted + "-" + post.getDate());

    if (isInserted > 0) {
        return true;
    } else {
        return false;
    }
}

public void addPosts(List<Post> posts) {
    for (int i = 0; i < posts.size(); i++) {
            addPost(posts.get(i));
    }
}

public List<Post> getPosts() {
    List<Post> posts = new ArrayList<>();

    SQLiteDatabase sqLiteDatabase = this.getReadableDatabase();
    Cursor cursor = sqLiteDatabase.rawQuery("SELECT * FROM " + POST_TABLE_NAME, null);
    cursor.moveToFirst();
    if (cursor.getCount() > 0) {
        while (!cursor.isAfterLast()) {
            Post post = new Post();
            post.setId(cursor.getInt(0));
            post.setPage(cursor.getString(1));
            post.setPage2(cursor.getString(2));
            post.setNiat(cursor.getString(3));
            post.setDate(cursor.getString(4));
            posts.add(post);
            cursor.moveToNext();
        }
    }
    cursor.close();
    sqLiteDatabase.close();
    System.out.println("rrrrrrrrrrrrrrr" + cursor.getCount());
    return posts;
}

Answer 1

我相信这段代码会导致getPosts方法失败，因为在调用cursor.getCount()时Cursor会被关闭。

cursor.close();
sqLiteDatabase.close();
System.out.println("rrrrrrrrrrrrrrr" + cursor.getCount());
return posts;

尝试将其更改为： -

System.out.println("rrrrrrrrrrrrrrr" + cursor.getCount()); //<<<< MOVED BEFORE CURSOR CLOSE
cursor.close();
sqLiteDatabase.close();
return posts;

关闭最近的应用程序后，Sqlite数据不会显示

1 个答案: