如何在Android中的SQLite数据库中以ListView显示数据

Question

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);
    createDatabase();
    c = db.rawQuery(fetch,null);
    c.moveToFirst();
    while(c.moveToNext()){
        id = c.getString(c.getColumnIndex("_id"));
        name =  c.getString(c.getColumnIndex("name"));
        number = c.getString(c.getColumnIndex("number"));
        //Toast.makeText(Main2Activity.this,id + name,Toast.LENGTH_LONG).show();
        from = new String[]{id, name, number};
        to = new int[]{R.id.label, R.id.numberq, R.id.num};
        adapter = new SimpleCursorAdapter(this,R.layout.layout,c,from,to,0);
    }
    ListView list = (ListView) findViewById(R.id.listview);
    list.setAdapter(adapter);
}
protected void createDatabase(){
    db = openOrCreateDatabase("PersonDB",Context.MODE_PRIVATE,null);
    db.execSQL("CREATE TABLE IF NOT EXISTS Person(_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, name VARCHAR, number VARCHAR);");

}

我试图在列表视图中显示数据，但它显示异常：“ java.lang.IllegalArgumentException：列'_id'不存在”

Answer 1

尝试这个

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        createDatabase();
        c = db.rawQuery(fetch,null);


            String[] from = new String[]{"_id","name","number"};
            int[] to = new int[]{R.id.label, R.id.numberq, R.id.num};
            adapter = new SimpleCursorAdapter(this,R.layout.layout,c,from,to,0);

        ListView list = (ListView) findViewById(R.id.listview);
        list.setAdapter(adapter);
    }
    protected void createDatabase(){
        db = openOrCreateDatabase("PersonDB",Context.MODE_PRIVATE,null);
        db.execSQL("CREATE TABLE IF NOT EXISTS Person(_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, name VARCHAR, number VARCHAR);");

    }

Answer 2

正如其他人指出的那样，将两个id名称都更改为id或_id

此外，使用SimpleCursorAdapter无需自己遍历Cursor，适配器可以为您完成此工作。

Cursor cursor = db.rawQuery(...);
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
        R.layout.layout, 
        cursor, 
        new String[]{"id", "name", "number"}, 
        new int[]{R.id.label, R.id.numberq, R.id.num});

ListView listView = (ListView) findViewById(R.id.list);
listView.setAdapter(adapter);

Answer 3

将其替换为您的代码：

    protected void createDatabase(){
    db = openOrCreateDatabase("PersonDB",Context.MODE_PRIVATE,null);
    db.execSQL("CREATE TABLE IF NOT EXISTS Person(_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, name VARCHAR, number VARCHAR);");

}

Answer 4

更换

id = c.getString(c.getColumnIndex("_id"));

通过

id = c.getString(c.getColumnIndex("id"));

Answer 5

表中id的列名称是id而不是 _id 。 如该行所示：

db.execSQL("CREATE TABLE IF NOT EXISTS Person(id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, name VARCHAR, number VARCHAR);");

因此，更换

id = c.getString(c.getColumnIndex("_id"));

与

id = c.getString(c.getColumnIndex("id"));