Question

大家早上好，我正在为我的数据库编写一个包含3个表的适配器：用户，问题，答案用户正在回答从DB生成的一些问题并插入答案我在SQLite浏览器上尝试了我的SQLite代码，它运行得很好，就像我的SQL查询一样。

我创建了一个包含名称，日期，问题和答案的类历史记录。然后我创建了一个包含ListView的activity_history，以及一个包含4个textViews的activity_adapter，类适配器：

public class MyAdapter extends ArrayAdapter<history> {
    private LayoutInflater mInflat;
    private ArrayList<history> hist;
    private int mVRessId;


    public MyAdapter (Context context, int ressId, ArrayList<history> hists){

        super(context,ressId,hists);
        this.hist =hist;
        mInflat = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        mVRessId =ressId;
    }

    public View getView(int position, View convertedView, ViewGroup parents){
        convertedView = mInflat.inflate(mVRessId,null);
        History histor = hist.get(position);



        if (histor != null){
            TextView name = (TextView) convertedView.findViewById(R.id.hname);
            TextView quest = (TextView) convertedView.findViewById(R.id.hques);
            TextView ans = (TextView) convertedView.findViewById(R.id.hans);
            TextView date = (TextView) convertedView.findViewById(R.id.hdate);

            if (name != null){
                name.setText(histor.getNom());
            }
            if (quest != null){
                quest.setText(histor.getQuest());
            }
            if (ans != null){
                name.setText(histor.getRep());
            }
            if (date != null){
                name.setText(histor.getDate().toString());
            }
        }
        return convertedView;
    }
}

在DatabaseHelper中，我创建了一个函数，使用我的SQL查询返回一个Cursor：

 public Cursor getTableHistoAsCursor() {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor data = db.rawQuery(" SELECT Q." + KEY_QUESTION + " , U." + KEY_NOM + " , U." + KEY_PRENOM + " , A." + KEY_DATE + " , A. " + KEY_REPONSE + " from " + TABLE_QUESTION + " Q, " + TABLE_USER + " U, " + TABLE_ANSWER + " A WHERE Q." + KEY_ID_QUESTION + " = A." + KEY_ID_QUESTION + " AND A." + KEY_MATRICULE + " = U." + KEY_MATRICULE, null);
        return data;
    }

历史课，我写了这段代码：

public class Historian extends AppCompatActivity {

    ModelHelper openhelper; //<<<< Note 1
    SimpleCursorAdapter mSCA;
    SQLiteDatabase db;
    Cursor mCsr;
    ListView mListView;
    ArrayList<Historique> histList;
    Historique histo;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_historique);
        mListView = (ListView) findViewById(R.id.lsthisto); //<<<< Note 3
        openhelper =  new ModelHelper(this);
        db = openhelper.getReadableDatabase();
        histList = new ArrayList<>();


        mCsr = openhelper.getTableHistoAsCursor();
        int rows = mCsr.getCount();
        if (rows == 0 ){
            Toast.makeText(Historian.this, "No histo", Toast.LENGTH_SHORT).show();
        } else {
            while (mCsr.moveToNext()){

                histo = new Historique(mCsr.getString(0),mCsr.getString(1), mCsr.getString(2),mCsr.getString(3));
                histList.add(histo);
            }

            MyAdapter adapter =  new MyAdapter (this, R.layout.adapter_view_layout,histList);

        }

问题在于，当我执行时，没有问题或错误编译，只是列表视图总是为空。谢谢你的帮助。

Answer 1

问题在于，当我执行时，没有问题或错误编译时，只是列表视图总是空的。

你错过了setAdapter到listView。在行

之后添加mListView .setAdapter(adapter);

MyAdapter adapter = new MyAdapter (this, R.layout.adapter_view_layout,histList);

四列适配器安卓工作室与SQLite数据库

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