Android的 - 光标没有找到列 [英] Android - Cursor not finding Column

问题描述

我试图从一个游标的结果，并把他们在为我创建的对象。在Eclipse中，它出现在光标返回单行（这正是我想要的），但是当我试图访问它，我得到一个错误。这里的code获取单行：

I'm trying to get the results from a Cursor and put them in into an Object that I created. In Eclipse, it appears the cursor is returning a single row (which is what I want) but when I try to access it, I get an error. Here's the code to fetch a single row:

public Object fetchIssue(long IssueNumber, int type){

    //Get query cursor.
    Cursor cursor = mDB.query(true, ISSUES_TABLE, ISSUES_COLUMN_ARRAY, COL_ISSUE_ID + "=" + IssueNumber, null, null, null, null, null);

    int iCount = cursor.getCount();

    if(cursor == null)
        return null;

    Object objOut = null;

    if(type == QUERY_TYPE_STRING_ARRAY){
        //Create Array to hold Issue Information.
        String[] IssueInfo = new String[3];
        IssueInfo[0] = String.valueOf(IssueNumber);
        IssueInfo[1] = cursor.getString(cursor.getColumnIndexOrThrow(COL_DATE_RECEIVED));
        IssueInfo[2] = cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_SUMMARY));
        IssueInfo[3] = cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_STATUS));
        IssueInfo[4] = cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_SUB_STATUS));
        IssueInfo[5] = cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_DESCRIPTION));
        objOut = IssueInfo;
    }
    else{
        //Create IssueInfo object.
        IssueInfo IssueInfo = new IssueInfo(
                    IssueNumber, "12/12/2000",
                    //cursor.getString(cursor.getColumnIndexOrThrow(COL_DATE_RECEIVED)),
                    cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_SUMMARY)),
                    cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_STATUS)),
                    cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_SUB_STATUS)),
                    cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_DESCRIPTION)));
        objOut = IssueInfo;
    }

    //Close cursor.
    cursor.close();

    //Return IssueInfo.
    return objOut;
}

ICOUNT返回1，如果我把游标变量，在变量窗口中，我可以看到所有的列：

iCount returns 1 and if I put the cursor variable in the "variables" window, I can see all the columns:

和在类的顶部，表列变量设置为相同的名称

and at the top of the class, the table column variables are set to the same name:

public static final String ISSUES_TABLE = "Issues";
public static final String COL_ISSUE_ID = "_id";
public static final String COL_DATE_RECEIVED = "DateReceived";
public static final String COL_ISSUE_STATUS = "IssueStatus";
public static final String COL_ISSUE_SUB_STATUS = "IssueSubStatus";
public static final String COL_ISSUE_SUMMARY = "IssueSummary";
public static final String COL_ISSUE_DESCRIPTION = "IssueDescription";

private static final String[] ISSUES_COLUMN_ARRAY = new String[]{
    COL_ISSUE_ID, COL_DATE_RECEIVED, COL_ISSUE_SUMMARY, 
    COL_ISSUE_STATUS, COL_ISSUE_SUB_STATUS, COL_ISSUE_DESCRIPTION};

该错误是发生在这条线：

The error is occuring on this line:

//Create IssueInfo object.
        IssueInfo IssueInfo = new IssueInfo(
                    IssueNumber, "12/12/2000",
                    //cursor.getString(cursor.getColumnIndexOrThrow(COL_DATE_RECEIVED)),
                    cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_SUMMARY)),
                    cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_STATUS)),
                    cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_SUB_STATUS)),
                    cursor.getString(cursor.getColumnIndexOrThrow(COL_ISSUE_DESCRIPTION)));

或任何该等行（你可以看到，我注释掉收到日期，并把正常的字符串值，在那里，它需要）。

or any of those lines (as you can see, I commented out the Date Received and put a normal string value in there, which it takes).

下面的错误：

03-13 09:06:42.370: E/AndroidRuntime(2324): FATAL EXCEPTION: AsyncTask #2
    03-13 09:06:42.370: E/AndroidRuntime(2324): java.lang.RuntimeException: An error occured while executing doInBackground()
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at android.os.AsyncTask$3.done(AsyncTask.java:278)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at java.lang.Thread.run(Thread.java:856)
    03-13 09:06:42.370: E/AndroidRuntime(2324): Caused by: android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 1
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at android.database.AbstractCursor.checkPosition(AbstractCursor.java:400)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:50)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at com.adacel.dashboard.DBAdapter.fetchIssue(DBAdapter.java:215)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at com.adacel.dashboard.IssueInfoCreator.fetchIssue(IssueInfoCreator.java:42)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at com.adacel.dashboard.ViewIssue.LoadIssueDetails(ViewIssue.java:73)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at com.adacel.dashboard.ViewIssue.access$0(ViewIssue.java:70)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at com.adacel.dashboard.ViewIssue$GetIssueDetailsTask.doInBackground(ViewIssue.java:96)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at com.adacel.dashboard.ViewIssue$GetIssueDetailsTask.doInBackground(ViewIssue.java:1)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at android.os.AsyncTask$2.call(AsyncTask.java:264)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
    03-13 09:06:42.370: E/AndroidRuntime(2324):     ... 4 more

任何帮助是极大AP preciated！

Any help is greatly appreciated!

推荐答案

始终将光标移动到一个元素，您查询后：

Always move the Cursor to an element, after you query it:

if(cursor == null)
    return null;
if(!cursor.moveToFirst()) //this will move the cursor to the first element
    return null;

如果您希望多行更好的方式来做到这一点是：

if you expect multiple rows a better way to do it is:

if(cursor != null) {
   cursor.move(-1);
   while(cursor.moveToNext()) {
      //do stuff
   }
}

这篇关于Android的 - 光标没有找到列的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！