Question

我很难将通过按钮点击存储的数据显示在ListView中保存在SqlLite数据库中。当我点击它以将数据添加到数据库时，它不会在按钮下方显示我想要的数据。

我的代码：

boolean hasMoreData = cursor.moveToFirst();
    while (hasMoreData) {
        // get the value out of each column
        long key = cursor.getLong(cursor.getColumnIndexOrThrow(MyDataEntry._ID));
        String studentID = cursor.getString(cursor.getColumnIndexOrThrow(MyDataEntry.STUDENT_ID_COLUMN));
        String studentGrade = cursor.getString(cursor.getColumnIndexOrThrow(MyDataEntry.STUDENT_GRADE_COLUMN));
        //For now, just print out the record to the log.      

        ArrayList<String> myList = new ArrayList<>();
        myList.add( " student id: "+ studentID);
        myList.add(" student grade : " +studentGrade);
        ArrayAdapter<String> myAdapter =
                new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1,myList);
        ListView listView = (ListView) findViewById(R.id.listView);
        listView.setAdapter(myAdapter);


        System.out.println("RECORD KEY: " + key + " student id: " + studentID + " student grade : " + studentGrade);




        //move on to the next row!
        hasMoreData = cursor.moveToNext();
    }

在模拟器中看起来像这样：

current display

我想要的是什么：

what i want it to look like

Answer 1

在循环外放置 ArrayAdapter 和 ListView 。

ArrayList<String> myList = new ArrayList<>();

boolean hasMoreData = cursor.moveToFirst();
while (hasMoreData) {
    long key = cursor.getLong(cursor.getColumnIndexOrThrow(MyDataEntry._ID));
    String studentID = cursor.getString(cursor.getColumnIndexOrThrow(MyDataEntry.STUDENT_ID_COLUMN));
    String studentGrade = cursor.getString(cursor.getColumnIndexOrThrow(MyDataEntry.STUDENT_GRADE_COLUMN));

    myList.add( " student id: "+ studentID);
    myList.add(" student grade : " +studentGrade);

    hasMoreData = cursor.moveToNext();
}   
ArrayAdapter<String> myAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, myList);
ListView listView = (ListView) findViewById(R.id.listView);
listView.setAdapter(myAdapter);

Answer 2

每次拨打ArrayList<String> myList = new ArrayList<>();和ArrayAdapter<String> myAdapter = new ArrayAdapter<String>();时，您都会重置列表。

删除ArrayList<String> myList = new ArrayList<>();

然后移动 ArrayAdapter<String> myAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1); ListView listView = (ListView) findViewById(R.id.listView); listView.setAdapter(myAdapter);

在您的循环上方，您将解决此问题

循环调用＆＃39; myAdapter.add（＆＃34;无论你想要什么＆＃34;）;＆＃39;然后myAdapter.notifyDataSetChanged()更新ui

在ListView Android中显示ArrayList

2 个答案: