问题描述
我正在从 firebase 实时数据库获取数据，并且在迭代数据快照时，当像这样将数据插入房间数据库时，我在第 493 行的行号处出现 java.util.concurrentmodificationexception at java.util.arraylist$itr.next 错误。
Inventory.getInstance(Inventory.this.getActivity(),1).InventoryDAO().InsertData(items);
private List<InventoryEntity_TableColums> message; // Class Variable
private synchronized void append_inventory_conversation(DataSnapshot dataSnapshot) {
Iterator iterator = dataSnapshot.getChildren().iterator();
String inventory_Msg,inventory_TO,inventory_FROM,inventory_TimeStamp,inventory_FCM_FROM,inventory_FCM_TO,inventory_Type,Random_ID,inventory_FROM_ID,inventory_Receiver_ID;
while (iterator.hasNext()) {
inventory_Msg = (String) ((DataSnapshot) iterator.next()).getValue();
inventory_FROM = (String) ((DataSnapshot) iterator.next()).getValue();
inventory_FROM_ID = (String) ((DataSnapshot) iterator.next()).getValue();
inventory_TO = (String) ((DataSnapshot) iterator.next()).getValue();
inventory_TimeStamp = (String) ((DataSnapshot) iterator.next()).getValue();
inventory_Type = (String) ((DataSnapshot) iterator.next()).getValue();
Random_ID = (String) ((DataSnapshot) iterator.next()).getValue();
inventory_FCM_FROM = (String) ((DataSnapshot) iterator.next()).getValue();
inventory_FCM_TO = (String) ((DataSnapshot) iterator.next()).getValue();
// return count of RANDOM ID in room
int hasValue = inventoryRoomDatabase.getInstance(getActivity(),1).inventoryDAO().CheckValueExist(Random_ID);
Log.d(TAG,"Has inventory " + hasValue);
if (hasValue == 0) {
inventoryEntity_TableColums inventoryEntity_tableColums;
if (inventory_Type.equals("1")) {
inventoryEntity_tableColums = new inventoryEntity_TableColums(Session.getUserID(),inventory_Msg,"1");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("2")) {
inventoryEntity_tableColums = new inventoryEntity_TableColums(Session.getUserID(),"2");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("3")) {
inventoryEntity_tableColums = new inventoryEntity_TableColums(Session.getUserID(),"3");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("4")) { //THIS IS FOR SEARCHED IMAGES NOT FOR GIF IMAGES
inventoryEntity_tableColums = new inventoryEntity_TableColums( Session.getUserID(),"4");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("5")) {
//Adding inventory Data Into Database
inventoryEntity_tableColums = new inventoryEntity_TableColums( Session.getUserID(),"5");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("6")) {
//Adding inventory Data Into Database
inventoryEntity_tableColums = new inventoryEntity_TableColums( Session.getUserID(),"6");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("7")) {
//Adding inventory Data Into Database
inventoryEntity_tableColums = new inventoryEntity_TableColums(Session.getUserID(),"7");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("8")) {
//Adding inventory Data Into Database
inventoryEntity_tableColums = new inventoryEntity_TableColums( Session.getUserID(),"8");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("9")) {
//Adding inventory Data Into Database
inventoryEntity_tableColums = new inventoryEntity_TableColums(Session.getUserID(),"9");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("10")) {
//Adding inventory Data Into Database
inventoryEntity_tableColums = new inventoryEntity_TableColums( Session.getUserID(),"10");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("11")) {
//Adding inventory Data Into Database
inventoryEntity_tableColums = new inventoryEntity_TableColums( Session.getUserID(),"11");
message.add(inventoryEntity_tableColums);
} else if (inventory_Type.equals("12")) {
inventoryEntity_tableColums = new inventoryEntity_TableColums( Session.getUserID(),"12");
message.add(inventoryEntity_tableColums);
Log.d(TAG,"Message Type Message" + inventory_Msg);
} else if (inventory_Type.equals("13")) {
inventoryEntity_tableColums = new inventoryEntity_TableColums( Session.getUserID(),"13");
message.add(inventoryEntity_tableColums);
}
}
}
new Thread(new Runnable() {
@Override
public void run() {
//THIS LINE WHERE I AM GETTING java.util.concurrentmodificationexception at java.util.arraylist$itr.next at insertInventory
inventoryRoomDatabase.getInstance(inventoryScreen.this.getActivity(),1).inventoryDAO().Insertinventory(message);
}
}).start();
}
Room 数据库的 InsertInventroy
@Insert(onConflict = OnConflictStrategy.IGnorE)
void Insertinventory(List<InventoryEntity_TableColums> inv);
解决方法
我假设在 insertinventory 方法中您使用迭代器迭代列表，并且您想向列表添加新元素。问题是你不能对修改后的列表使用相同的迭代器。