Kotlin of Android cultivation manual - several ways to write a custom view

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Premise

This is what Xiao Kong insisted on writing Android Novice series , Welcome to taste .

bosses （√）

Novice （√√√）

Practice process

Use Kotlin Not used to it , Take notes .
There are three ways

Mode one

recommend , Note that the first two construction parameters are this, instead of super

class WaveViewKotlin: View{
    
    constructor(context: Context?) :this(context,null)
    constructor(context: Context?, attrs: AttributeSet?) :this(context,attrs,0)
    constructor(context: Context?, attrs: AttributeSet?, defStyleAttr: Int) : super(context, attrs, defStyleAttr)
    init {
    
        // Initialization method 
    }
    override fun onDraw(canvas: Canvas) {
    
      
    }
}

perhaps

class WaveViewKotlin: View{
    
    constructor(context: Context?, attrs: AttributeSet?) :super(context,attrs)
    init {
    
        // Initialization method 
    }
    override fun onDraw(canvas: Canvas) {
    
      
    }
}

Mode two

The other one parameter and three parameters are infeasible

class WaveViewKotlin(context: Context?, attrs: AttributeSet?) : View(context, attrs) {
    
    init {
    
        // Initialization method 
    }
    override fun onDraw(canvas: Canvas) {
    
      
    }
}

Mode three

The premise is that the project's build In the configuration kotlin Plug in for .

class WaveViewKotlin @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) : View(context, attrs, defStyleAttr){
    
    init {
    
        // Initialization method 
    }
    override fun onDraw(canvas: Canvas) {
    
      
    }
}

other

author ： Xiaokong and Xiaozhi Xiaokong
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