前言

说完了建造者模式，那就该提提工厂模式了

工厂模式与建造者模式的差别

因为这2个还是挺相似的，都是生成一个我们想要的东西，所以还是得说清楚的：
工厂模式：直接生成一个可用的产品

// 如bitmapFactory
val bitmap = BitmapFactory.decodeFile(filePath)b

建造者模式：配置相关参数生成一个我们想要的产品

//如AlertDialog
 val builder = AlertDialog.Builder(this)
 val dialog = builder.setTitle(xxxx)
            .setIcon(xxxx)
            .setIcon(XXX)
            .setXXX(xxx)
            .create()
            .show()

正文

对于工厂模式来说，工厂模式就是直接生成我们想要的东西
先来个简单的吧

 abstract class Fruits {
        abstract fun eat()
    }
    
    class Apple : Fruits(){
        override fun eat() {
            
        }
    }
    
    class Banana : Fruits(){
        override fun eat() {
            
        }
    }
    
    class FruitsFactory{
        
        companion object {
            val APPLE = "apple"
            val BANANA = "banana"
        }
        
        fun createFruits(type: String): Fruits?{
            when(type){
                APPLE -> return Apple()
                BANANA -> return Banana()
            }
            return null
        }
    }
//使用
  val fruitsFactory = FruitsFactory()
  val apple = fruitsFactory.createFruits(FruitsFactory.APPLE)
  apple?.eat()

除了简单工厂之外，还有个抽象工厂
就是你的工厂多了几个接口实现

abstract class Fruits {
        abstract fun eat()
    }

    class Apple : Fruits(){
        override fun eat() {

        }
    }

    class Banana : Fruits(){
        override fun eat() {

        }
    }

    abstract class Factory{
        abstract fun createApple(): Fruits
        abstract fun createBanana(): Fruits
    }
    
    class SimpleFruitsFactory : Factory(){
        override fun createApple(): Fruits {
            return Apple()
        }

        override fun createBanana(): Fruits {
            return Banana()
        }

    }
    
    class GifeFruitsFactory : Factory(){
        override fun createApple(): Fruits {
            return Apple()
        }

        override fun createBanana(): Fruits {
            return Banana()
        }
    }
//使用
        val simpleFruitsFactory = SimpleFruitsFactory()
        val simpleApple = simpleFruitsFactory.createApple()
        val gifeFruitsFactory = GifeFruitsFactory()
        val giftBanana = gifeFruitsFactory.createBanana()