如果 SQLite 游标没有结果，应用程序会崩溃

Question

我有一个使用游标运行 SQlite 查询的应用程序。

    public Cursor totaltrips(){
    Cursor cursor = database.rawQuery("SELECT * AS TTotal FROM " + DatabaseHelper.TABLE_NAME, null);
    return cursor;
}

结果存储到一个最多有 5 个值的 Arraylist 中。如果数据库中没有记录，应用程序就会崩溃。如果我有一个或多个数据库条目，它就可以正常工作。有谁知道在没有数据库条目时如何阻止它崩溃？

 // get column value
    if (Distance.moveToNext())
        result = String.valueOf(Distance.getDouble(Distance.getColumnIndex("myTotal")));

    tnmView.setText(result);

    List<String> distancearray = new ArrayList<String>();
    Cursor cursor =  dbManager.totaldistance();


    do{
        distancearray.add(cursor.getString(1));
    }while ((cursor.moveToNext()));
    ttrips = cursor.getCount();
    Log.i("Graph", "TTRIPS = " + ttrips);

    // Be sure here to have at least the 5 desired elements into the list
    while(distancearray.size() < 5){
        distancearray.add("0");
    }

应用崩溃并出现错误

android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0

在线

do{
        distancearray.add(cursor.getString(1));
    }while ((cursor.moveToNext()));

Answer 1

检查光标是否真的有结果，例如尝试这样的事情：

int numResults = cursor.getCount();
if (numResults > 0) {
    do {
        distancearray.add(cursor.getString(1));
    } while ((cursor.moveToNext()));
}

Answer 2

替换

do{
    distancearray.add(cursor.getString(1));
}while ((cursor.moveToNext()));

和

if (cursor != null) {
    while (cursor.moveToNext()) {
        distancearray.add(cursor.getString(1));
    }
    cursor.close();
}

Answer 3

使用后检查游标是否为空并且有多个value.Close游标。

if(cursor!=null&&cursor.getCount()>0){
cursor.moveToFirst();
while(cursor.hasNext()){

//do stuff here
}

cursor.close();
}

如果 SQLite 游标没有结果，应用程序会崩溃

App crashes if SQLite cursor has no results

sqlite

android

arraylist

android-sqlite