dart语言和flutter学习——Dart语言学习

一、编译环境 IntelliJ IDEA+安装Dart插件及下载并配置DartSDK路径，创建Dart项目

二、Dart语言学习记录

学习感受：总体感觉Dart的语法没什么特殊的地方，基本和java和JavaScript差不多，学习起来可能花个几小时看完官方文档并敲一遍就可以了。

还未学习完成，后面持续学习

2.1基本的变量简单语法的了解

void main(){
  print("hello world"); //注释
  testDart();
  testDartNumberType();
  testOperate();
  testCondition();
  testTypeConvert();

}


void testDart() {
  //变量
  var name = "dart";
  String nameStr = "Dart";
  print("your name is " + name);
  print("your name is " + nameStr);
  int age = 25;
  var ageNum = 25;
  print(age);
  print(ageNum);
  
  //常量
  const PI = 3.1415926;
  print(PI);
  final PINUM = 3.1415;
  print(PINUM);
  final DATA = new DateTime.now();
  print(DATA);
}


void testDartNumberType(){
  //1、字符串类型, 两种定义方法
  var str1 = "star1";
  var str2 = 'str2';
  print(str1);
  print(str2);
  String s1 = "s1";
  print(s1);
  String s2 = '''line1
  lin2
  lin3''';
  print(s2);
  print(str1 + s1);
  //2、数值类型：int 和 double
  int age = 1;
  double height = 1.7;
  print(age);
  print(height);
  //3、 bool 类型
  bool flag = true;
  print(flag);
  if(flag) {
    print("it is true");
  } else {
    print("it is false");
  }
  //4、集合类型 List， 两种定义方法
  var list1 = ["java", "python", 20];
  print(list1);
  print(list1[1]);
  var list2 = ["java", "dart"];
  list2.add("python");
  print(list2);
  var list3 = List.filled(3, ""); //创建固定长度的集合，add不能超过集合长度
  print(list3);
  var list4 = ["1", '2']; //[]创建的集合可以修改长度
  list4.length = 0;
  print(list4);
  var list5 = List.filled(2, "language");
  //5、map类型
  var person = {
    "name": "kanghui",
    "age":12
  };
  print(person);
  print(person["age"]);
  var person1 = new Map();
  person1["name"] = "dart";
  person1["age"] = 5;
  print(person1);
  //6、类型判断 is关键字
  var a = "123";
  if(a is String) {
    print("a is a string");
  }
}


void testOperate(){
  int age = 20;
  String sex = "man";
  //字符串的判等使用==即可
  if(age == 20 && sex == "man"){
      print("ok");
  }

  int a =  0;
  int b = a ?? 2; //两个问号代表空判断，如a不为空则把a赋值给b，否则把2赋值给b
  print(b);
}


void testCondition(){
  bool flag = true;
  print(flag ? "1" : "0");

  int a = 1;
  int b = a ?? 2; //两个问号代表空判断，如a不为空则把a赋值给b，否则把2赋值给b
  print(b);
}


void testTypeConvert(){
  String str1 = "123";
  int num1 = int.parse(str1);
  print(num1);

  double d1 = double.parse(str1);
  print(d1);

  int num2 = 333;
  String str2 = num2.toString();
  print(str2);
  print(str2 is String);
  print(str2.isEmpty);
}