当我尝试向应用程序中添加分数/点时，我收到此错误：NumberFormatException: null。
我为此创建了单独的表，因为我需要多个表。 我不知道问题出在哪里，所以谢谢大家。
if(count==4) {
my_db=new DBHelper(this);
sqdb = my_db.getWritableDatabase();
Cursor c_oldPoints= sqdb.query(DBHelper.TABLE_NAME2,null,DBHelper.NICKNAME+"=?",new String[]{Username},null,null,null);
int col_Points=c_oldPoints.getColumnIndex(DBHelper.POINTS);
c_oldPoints.moveToFirst();
while (!c_oldPoints.isAfterLast())
{
OldPoints=c_oldPoints.getString(col_Points);
c_oldPoints.moveToNext();
}
sqdb.close();
int OldP = Integer.parseInt(OldPoints);
OldP+=countPoints;
String SoldP = Integer.toString(OldP);
my_db=new DBHelper(this);
sqdb = my_db.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(my_db.POINTS,SoldP);
Cursor c = sqdb.query(DBHelper.TABLE_NAME2,null,DBHelper.NICKNAME+"=?",new String[]{Username},null,null,null);
c.moveToFirst();
while (!c.isAfterLast())
{
sqdb.update(DBHelper.TABLE_NAME2,cv, DBHelper.POINTS+"=?",new String[]{OldPoints});
c.moveToNext();
}
sqdb.close();
countPoints=0;
}
这是日志猫：-
2019-05-15 18:18:14.101 8513-8513/com.example.user.soundsequ E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.user.soundsequ, PID: 8513
java.lang.NumberFormatException: null
at java.lang.Integer.parseInt(Integer.java:483)
at java.lang.Integer.parseInt(Integer.java:556)
at com.example.user.soundsequ.Game.onClick(Game.java:353)
at android.view.View.performClick(View.java:5637)
at android.view.View$PerformClick.run(View.java:22429)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
答案 0 :(得分：0)
错误似乎在此行
int OldP = Integer.parseInt(OldPoints);
错误是说OldPoints的值不是可以转换为整数的字符串，例如如果它是A或null；
因此，从POINTS列中提取的值不是数字，或者Username的值与行中的NICKNAME列不匹配。在这种情况下，OldPoints将是循环之前设置的任何值。
由于数据本身不可用，您需要确定两种情况中的哪一种导致了问题。
我建议添加一些“登录”以确定哪个。
例如通过使用类似：-
OldPoints = "my debugging value";
Log.d("MYDEBUGGING","OldPoints, before doing anything is " + OldPoints);
Cursor c_oldPoints= sqdb.query(DBHelper.TABLE_NAME2,null,DBHelper.NICKNAME+"=?",new String[]{Username},null,null,null);
int col_Points=c_oldPoints.getColumnIndex(DBHelper.POINTS);
c_oldPoints.moveToFirst();
while (!c_oldPoints.isAfterLast())
{
OldPoints=c_oldPoints.getString(col_Points);
c_oldPoints.moveToNext();
Log.d("MYDEBUGGING","Extracted the value " + OldPoints + " from position + String.valueOf(c_oldPoints.getPosition());
}
sqdb.close();
Log.d("MYDEBUGGING","Trying to convert the value " + OldPoints + " to an integer");
int OldP = Integer.parseInt(OldPoints);
您也无法进行上述更改并添加一个断点（在最初指示的行上），然后使用“运行/调试”应用程序并检查变量（或在适当的位置使用多个断点）。您可能会发现这对于调试Debug your app很有用。
以下代码可防止出现异常，也可防止尝试更新不存在的用户：-
if (count == 4) {
SQLiteDatabase sqdb = my_db.getWritableDatabase();
Cursor c_oldPoints= sqdb.query(
DBHelper.TABLE_NAME2,null,
DBHelper.NICKNAME+"=?",
new String[]{Username},
null,null,null
);
int col_Points=c_oldPoints.getColumnIndex(DBHelper.POINTS);
if (c_oldPoints.moveToFirst()) {
Oldpoints = c_oldPoints.getString(col_Points);
//Oldpoints = "oops";
int OldP = 0;
boolean can_convert_to_int = true;
try {
OldP = Integer.parseInt(Oldpoints) + countPoints;
can_convert_to_int = true;
} catch (NumberFormatException e) {
e.printStackTrace(); //TODO not necessary probably remove. just for checking the log
}
if (can_convert_to_int) {
ContentValues cv = new ContentValues();
cv.put(DBHelper.POINTS,OldP);
sqdb.update(DBHelper.TABLE_NAME2,cv, DBHelper.NICKNAME + "=?", new String[]{Username});
}
} else {
Log.d("NICKNAMENOTFOUND","No row was found when attemtping to get the old score for User " + Username);
}
}
我建议您向DBHelper类添加几个方法，这些方法是：-
public int increasePoints(String user, int points_to_add) {
SQLiteDatabase db = this.getWritableDatabase();
SQLiteStatement sql = db.compileStatement(
"UPDATE " + TABLE_NAME2 +
" SET " + POINTS + "=" + POINTS + " +? " +
"WHERE "+ NICKNAME + "=?"
);
sql.bindLong(1,points_to_add);
sql.bindString(2,user);
return sql.executeUpdateDelete();
}
public int getPoints(String user) {
SQLiteDatabase db = this.getWritableDatabase();
int rv = -1;
String whereclause = NICKNAME + "=?";
String[] whereargs = new String[]{user};
Cursor csr = db.query(TABLE_NAME2,new String[]{POINTS},whereclause,whereargs,null,null,null);
if (csr.moveToFirst()) {
rv = csr.getInt(csr.getColumnIndex(POINTS));
}
csr.close();
return rv;
}
第一种方法 increasePoints 通过UPDATE sql语句执行对点的更改，并且不需要将提取为字符串的点转换为整数。它返回已更新的行数（如果NICKNAME列始终是唯一值，则返回1；如果未更新，则返回0）。
第二种方法 getPoints 就是说的，它获取给定用户的分数，如果该用户不存在，它将返回-1。
您的代码可能是：-
if (count == 4) {
boolean updated = false; //TODO remove when happy
int old_points = my_db.getPoints(Username); //TODO remove when happy
if (my_db.increasePoints(Username,countPoints) > 0) {
updated = true;
}
int new_points = my_db.getPoints(Username); //TODO remove when happy
//TODO remove following code when happy
String result = "The result of the attempt to update the points for user " + Username;
if (updated) {
result = result + " was successful. ";
} else {
result = result + " was unsuccessful.";
}
Log.d("POINTSINCREASE",result +
" Points were " + String.valueOf(old_points) + " points are now " + String.valueOf(new_points));
}
注意，其中//TODO remove when happy被编码，这些行仅用于测试，因此上面的内容可能是：-
if (count == 4) {
my_db.increasePoints(Username,countPoints);
}