Question

如果它不包含单个行（空表），我需要向表中插入值。如果表中已存在数据，则无需插入。我使用了以下代码。

sampleDB = this.openOrCreateDatabase(SAMPLE_DB_NAME, MODE_PRIVATE, null);
        sampleDB.execSQL("CREATE TABLE IF NOT EXISTS " + SAMPLE_TABLE_NAME
                + " (rowid INT , songname VARCHAR," + "  count INT);");
        int len = MP3Activity.songlist.size();
        Log.v("songlist len", Integer.toString(len));           
        cur = sampleDB.rawQuery("SELECT COUNT(*)  FROM "+ SAMPLE_TABLE_NAME ,null);
        if (cur != null) {
                if(cur.getInt(0)<=1) //exception at this line.
                    {
                        for (int s = 0; s < MP3Activity.songlist.size(); s++) {
                            Log.v("Before insert", "1");
                                sampleDB.execSQL("INSERT INTO " + SAMPLE_TABLE_NAME + " Values ("
                                        + row_id++ + ",\"" + MP3Activity.songlist.get(s) + "\","
                                        + count + ");");        
                                Log.v("After insert", "1");
                            }
                    }
                    else
                    {
                        Log.v("inside else......","");
                    }

            }           

        cur.close();        

         c = sampleDB.rawQuery("SELECT songname, count, rowid FROM "
                + SAMPLE_TABLE_NAME + " where count=0 ", null);

        if (c != null) {
            if (c.moveToFirst()) {
                do {
                    String songName = c.getString(c.getColumnIndex("songname"));
                    int count = c.getInt(c.getColumnIndex("count"));
                    int rid=c.getInt(c.getColumnIndex("rowid"));
                    results.add("Rowid: " + rid + ",Song Name: " + songName + ",Count: " + count);
                } while (c.moveToNext());
            }
        }
        c.close();
        int reslen = results.size();
        Log.v("Length of result", Integer.toString(reslen));

        for (int i = 0; i < results.size(); i++) {
            Log.v("Element in result", results.get(i));
        }
        /*for (int k = 0; k < results.size(); k++) {

            if (sampleDB != null)
                sampleDB.execSQL("DELETE  FROM " + SAMPLE_TABLE_NAME);

        }*/
        sampleDB.close();

我遇到以下异常。

01-19 15:22:42.059: E/AndroidRuntime(464): Caused by: android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 1
01-19 15:22:42.059: E/AndroidRuntime(464):  at android.database.AbstractCursor.checkPosition(AbstractCursor.java:580)
01-19 15:22:42.059: E/AndroidRuntime(464):  at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:172)
01-19 15:22:42.059: E/AndroidRuntime(464):  at android.database.AbstractWindowedCursor.getInt(AbstractWindowedCursor.java:84)
01-19 15:22:42.059: E/AndroidRuntime(464):  at com.mp3.Frequent.onCreate(Frequent.java:46)
01-19 15:22:42.059: E/AndroidRuntime(464):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
01-19 15:22:42.059: E/AndroidRuntime(464):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364)

Answer 1

您需要将光标移动到第一个元素（如果有），就像您为第二个查询所做的那样：即在访问列值的游标之前检查c.moveToFirst（）的结果。

Answer 2

如果您的表为空，那么如何在此行中获取列索引

if(cur.getInt(0)<=1) //exception at this line.

所以用

替换它

if(cur.getCount()<=1) //exception at this line.

编辑：
而不是检查上述条件，你也可以像这样检查

if(cur.getCount()>0) //exception at this line.
       {
//Already Inserted value
     }
         else
            {
                    for (int s = 0; s < MP3Activity.songlist.size(); s++) {
                        Log.v("Before insert", "1");
                            sampleDB.execSQL("INSERT INTO " + SAMPLE_TABLE_NAME + " Values ("
                                    + row_id++ + ",\"" + MP3Activity.songlist.get(s) + "\","
                                    + count + ");");        
                            Log.v("After insert", "1");
                        }

                }

如果表为空，需要帮助向表中插入值

2 个答案: