Question

我的光标

    Cursor c= db.query(DBHelper.EXAM_DATA,new String [] {DBHelper.EXAM,DBHelper.FILE}, null,null, null, null, null);

光标循环

c.moveToFirst();
    do
    {
        name = c.getString(0);
        file = c.getString(1);
        Toast.makeText(this, name + "   "+file  ,Toast.LENGTH_LONG).show();
        adapter = new SimpleCursorAdapter(this, R.layout.row_reasoning, c, new String [] {file}, new int [] {R.id.txtList});
        LvReasoning.setAdapter(adapter);
    }while(c.moveToNext());

Logcat显示此错误

01-20 16:33:55.154: E/AndroidRuntime(2426): FATAL EXCEPTION: main
01-20 16:33:55.154: E/AndroidRuntime(2426): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.androidhive.xmlparsing/com.androidhive.xmlparsing.ListReasoning}: java.lang.IllegalArgumentException: column '_id' does not exist

我的表有_id列但我不知道如何解决此错误

Answer 1

c.moveToFirst();
    do
    {
        name = c.getString(0);
        file = c.getString(1);
        Toast.makeText(this, name + "   "+file  ,Toast.LENGTH_LONG).show();
        adapter = new SimpleCursorAdapter(this, R.layout.row_reasoning, c, new String [] {DBHelper.FILE}, new int [] {R.id.txtList});

    }while(c.moveToNext());
    LvReasoning.setAdapter(adapter);

我用过这个，这就是工作。我已经通过DBHelper表字段名称和它的工作正常..但我真的不知道为什么代码不起作用...

Answer 2

提供给SimpleCursorAdapter的游标必须包含名为_id的列。它存在于表中的事实是不够的，你必须选择它，所以将它包含在返回的列列表中：

Cursor c= db.query(DBHelper.EXAM_DATA,new String [] {"_id", DBHelper.EXAM, DBHelper.FILE}, null,null, null, null, null);

您还需要实例化并设置适配器一次。将这些语句移到while循环之外（如果不需要为每个游标行的内容加密，可以完全删除循环）：

adapter = new SimpleCursorAdapter(this, R.layout.row_reasoning, c, new String [] {file}, new int [] {R.id.txtList});
LvReasoning.setAdapter(adapter);

对于每个游标行，适配器然后将列'file'的值映射到R.layout.row_reasoning中的R.id.txtList。

简单光标适配器抛出异常非法参数异常？

2 个答案: