[fluent] dart data type number type (DART file creation | num type | int type | double type | num related API)

I . establish Dart file

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establish Flutter application : This is created before Flutter application ;

establish Dart file : Right click on the lib -> New -> Dart File , Enter... In the pop-up dialog box Dart File name is enough ;

Use templates : Enter in file stful , choice New Stateful widge Templates , You can use this template ;

The completion code : The main codes are in Widget build(BuildContext context) { } Method implementation ;

import 'package:flutter/material.dart';class DartType_Number extends StatefulWidget { 
      @override  _DartType_NumberState createState() => _DartType_NumberState();}class _DartType_NumberState extends State<DartType_Number> { 
      @override  Widget build(BuildContext context) { 
        return Container();  }}

II . num / int / double Numeric type

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1 . num And int and double The relationship between :num It's the number type , It has two subclasses , int and double type ;

2 . num Type variable : It can be accepted that Integer variables , You can also accept floating-point variables ;

3 . num Examples of type usage :

/* num  Numeric type   Is the parent of numeric type  num  Two subclasses of  : ① int , ② double num  Type variables can be assigned   Integer types  ,  You can also assign values   Floating point type  */num num_1 = 1.0;  // Accept floating point types num num_2 = 1;    // Accept integer int int_1 = -1;    //int  Type can only accept integer types double double_1 = 3.14; //double  Type can only accept floating-point types // Print the four values above print("num_1 : $num_1 num_2 : $num_2 int_1 : $int_1 double_1 : $double_1");

4 . Execution results :

 num_1 : 1.0 num_2 : 1 int_1 : -1 double_1 : 3.14

III . Number type correlation API

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1 . Find the absolute value : call num Of abs() Method , O the num The absolute value of the type ;

2 . Digital type conversion : call num Of toInt() , toDouble() , toString() And other methods can realize digital type conversion ;

3 . complete Dart Component code example :

import 'package:flutter/material.dart';class DartType_Number extends StatefulWidget { 
      @override  _DartType_NumberState createState() => _DartType_NumberState();}class _DartType_NumberState extends State<DartType_Number> { 
      @override  Widget build(BuildContext context) { 
        /* num  Numeric type   Is the parent of numeric type  num  Two subclasses of  : ① int , ② double num  Type variables can be assigned   Integer types  ,  You can also assign values   Floating point type  */    num num_1 = 1.0;  // Accept floating point types     num num_2 = 1;    // Accept integer     int int_1 = -1;    //int  Type can only accept integer types     double double_1 = 3.14; //double  Type can only accept floating-point types     // Print the four values above     print("num_1 : $num_1 num_2 : $num_2 int_1 : $int_1 double_1 : $double_1");        /*  Number type common  API 1 .  Find the absolute value  :  call  num  Of  abs()  Method  ,  O the  num  The absolute value of the type  2 .  Digital type conversion  :  call  num  Of  toInt() , toDouble() , toString()  And other methods can realize digital type conversion  */    print("$int_1  The absolute value  : ${int_1.abs()}");    print("$int_1  To  double : ${int_1.toDouble()}");    print("$double_1  To  int : ${double_1.toInt()}");    return Container(child: Text(' Numeric type '));  }}

4 . Execution results :

num_1 : 1.0 num_2 : 1 int_1 : -1 double_1 : 3.14-1  The absolute value  : 1-1  To  double : -1.03.14  To  int : 3