Flutter中的List数组如何避免插入重复数据

List<int> fixedLengthList = new List(2);
for(int i=0;i<2;i++){
  print("索引为${i}的值${fixedLengthList[i]}");
}

List<int> fixedLengthList = new List(2);
//改变固定数组长度
fixedLengthList.length=30;

List<int> fixedLengthList = new List(2);
///执行添加数据操作
fixedLengthList.add(0);
fixedLengthList.add(1);

List<int> fixedLengthList = new List(2);
  fixedLengthList[0]=1;
  fixedLengthList[1]=2;
///添加数据
fixedLengthList.addAll([3,4]);

List<int> fixedLengthList = new List(2);
//执行插入数据
fixedLengthList.insert(0, 0);

 List<int> fixedLengthList = new List(2);
  ///执行删除操作
  fixedLengthList.removeLast();

List<int> fixedLengthList = new List(2);
  ///执行删除操作
  fixedLengthList.removeAt(0);

 List<int> fixedLengthList = new List(2);
  fixedLengthList[0]=1;
  fixedLengthList[1]=2;
///删除包含索引0和1范围内数据
fixedLengthList.removeRange(0, 1);

List<int> fixedLengthList = new List(2);
  fixedLengthList[0]=1;
  fixedLengthList[1]=2;
///删除索引0-1,然后在进行替换删除索引值
fixedLengthList.replaceRange(0, 1, [3,4]);

List<int> fixedLengthList = new List(2);
///执行清除数据操作
fixedLengthList.clear();

List<int> fixedLengthList = new List(2);
fixedLengthList[0]=1;
fixedLengthList[1]=2;

///执行截取指定范围的数组
fixedLengthList.sublist(0);
///排序
fixedLengthList..sort((a, b) => a.compareTo(b));
///
fixedLengthList.setRange(0, 1, [3,4],0);
///索引0-1范围的值不包括1,修改成3
fixedLengthList.fillRange(0, 1,3);

List<int> fixedLengthList = [];

  //改变数组长度
  fixedLengthList.length=2;
  ///执行添加数据操作
  fixedLengthList.add(0);
  fixedLengthList.add(1);
  fixedLengthList[0]=1;
  fixedLengthList[1]=2;
  ///添加数据
  fixedLengthList.addAll([3,4]);
  //执行插入数据
  fixedLengthList.insert(0, 0);
  ///执行删除操作
  fixedLengthList.removeLast();
  ///执行删除操作
  fixedLengthList.removeAt(0);
  ///删除包含索引0和1范围内数据
  fixedLengthList.removeRange(0, 1);
  ///删除索引0-1,然后在进行替换删除索引值
  fixedLengthList.replaceRange(0, 1, [3,4]);

  fixedLengthList.sublist(0);
  fixedLengthList..sort((a, b) => a.compareTo(b));
  fixedLengthList.setRange(0, 1, [3,4],0);
  fixedLengthList.fillRange(0, 1,3);

  ///执行清除数据操作
  fixedLengthList.clear();

List<int> listInts = [];

 void addIntData(int addValue){
  bool isContainer=listInts.contains(addValue);
  if(!isContainer){
   listInts.add(addValue);
  }
  print("数组长度${listInts.length}");
 }

List<double> listDouble = [];

 void addDoubleData(double addValue){
  bool isContainer=listDouble.contains(addValue);
  if(!isContainer){
   listDouble.add(addValue);
  }
  print("数组长度${listDouble.length}");
 }

 List<String> listStrings = [];

 void addStringData(String addValue){
  bool isContainer=listStrings.contains(addValue);
  if(!isContainer){
   listStrings.add(addValue);
  }
  print("数组长度${listStrings.length}");
 }

 List<bool> listBool = [];

 void addBoolData(bool addValue){
  bool isContainer=listBool.contains(addValue);
  if(!isContainer){
   listBool.add(addValue);
  }
  print("数组长度${listBool.length}");
 }

class A{
 String a;
 int b;

 A(this.a, this.b);
}

 List<A> listAs = [];

 void addAData(A addValue){

  int length=listAs.length;
  if(length==0){
   listAs.add(addValue);
  }else {
   for (int i = 0; i < length; i++) {
    A a = listAs[i];
    if (a.a != addValue.a && a.b != addValue.b) {
     listAs.add(addValue);
    }
   }
  }
  print("数组长度${listAs.length}");
 }

List<A> listAs = [];
Set<A> setAs=new Set<A>();

void addASData(A addValue){
  if(listAs.length==0) {
   listAs.add(addValue);
   setAs.addAll(listAs);
  }else{
   listAs.add(addValue);
  }
  List<A> list=setAs.toList();
  print("数组长度${list.length}");
}

addASData(new A("a", 0));