前言:作为一个安卓开发的老鸟,一步步从eclipse到AS开发安卓app,再到NDK开发,不断的更新,不断的学习,现如今Google把安卓的第一开发语言换成了Kotlin,所以我们也要紧跟Google步伐,转战kotlin,接下来我会带领大家快速入门kotlin开发。
1.1函数
fun main(args:Array<String>){
printstar(10)
printstar(15)
printstar()
}
fun printstar(i:Int){
println("*"+i)
}
fun printstar(){
println("**")
}
1.2函数-加减乘除
fun main(args:Array<String>){
var m = 10
var n = 5
var p = plus(m, n)
println("m+n = "+p)
var s = sub(m, n)
println("m-n = "+s)
var mu = mutl(m, n)
println("mxn = "+mu)
var d = div(m, n)
println("m/n = "+d)
}
//fun 函数名字(第一个int参数,第二个int参数)返回一个int值
fun plus(a:Int, b:Int):Int{
return a+b;
}
fun sub(a:Int, b:Int):Int{
return a-b;
}
fun mutl(a:Int, b:Int):Int{
return a*b;
}
fun div(a:Int, b:Int):Int{
return a/b;
}
2.boolean类型
fun main(args:Array<String>){
var num1 = 4
var num2 = 6
println(num1 < num2)
println(num1 > num2)
var num3 = Math.sqrt(5.0) - Math.sqrt(4.0)
var num4 = Math.sqrt(4.0) - Math.sqrt(3.0)
println("num3 = "+num3)
println("num4 = "+num4)
println(num3 > num4)
println(num3 < num4)
}
3.字符串操作(日记生成)
fun main(args:Array<String>){
var diary = diaryGenerater("北京")
println(diary);
diary = diaryGenerater("杭州西湖")
println(diary);
}
fun diaryGenerater(placeName:String):String{
var temp = "我想去${placeName},所以要在百度搜<<${placeName}>> ${placeName.length}个字。"
return temp
}
4.1if语句
//if else
fun main(args:Array<String>){
var m = 10
var n = 20
println("${m}和${n}中大的数字是${retunBigNumber(m,n)}")
}
fun retunBigNumber(a:Int,b:Int):Int{
if(a>b){
return a
}else{
return b
}
}
4.2if语句2
fun main(args:Array<String>){
var face = checkFace(90)
println(face)
face = checkFace(60)
println(face)
}
fun checkFace(score:Int):String{
if(score>80){
return "帅哥或者美女"
}else{
return "不是帅哥也不是美女"
}
}
5.字符串比较
fun main(args:Array<String>){
var str1 = "fly"
var str2 = "FLY"
println(str1.equals(str2))
println(str1.equals(str2,true)) //忽略大小写
}
6.空值处理
fun main(args:Array<String>){
var str1 = heat("123")
println(str1)
var str2 = heat(null)
println(str2) //忽略大小写
}
//添加一个问号,表示可以传入一个null字符串
fun heat(str:String?):String{
return "heat:"+str
}
7.when语句
fun main(args:Array<String>){
gradeStudent(90)
}
fun gradeStudent(score:Int){
when(score){
90 -> println("优秀")
70 -> println("还可以")
else -> println("加油")
}
}
8.1loop和Range
fun main(args: Array<String>){
var nums = 1 .. 100
var result = 0
for(num in nums){
println(num)
result = result + num
}
println("1到100的结果是${result}")
}
8.2loop和Range
fun main(args: Array<String>){
var nums = 1 until 100
var result = 0
for(num in nums){
println(num)
result = result + num
}
println("1 until 100的结果是${result}")
}
8.3loop和Range
fun main(args: Array<String>){
var nums = 1 .. 100
for(num in nums step 2){
println(num)
}
var nums2 = nums.reversed();
for(num2 in nums2){
println(num2)
}
}
9.list
fun main(args: Array<String>){
var lists = listOf("北京","上海","杭州","深圳")
for ((i,e) in lists.withIndex()){
println("$i $e")
}
}
10.map
import java.util.TreeMap
fun main(args: Array<String>){
var map = TreeMap<String, String>()
map["好好"] = "good good"
map["学习"] = "study"
map["天天"] = "day day"
map["向上"] = "up"
println(map["学习"])
}
结束。。。。明天继续。