创建一个FindView的trait
定义findView方法简化了findViewById(id).asInstanceOf
同时定义implicit简化了setOnClickListener

package org.noahx.scalaandroid

import android.app.Activity
import android.view.View

trait FindView extends Activity {

  def findView[WidgetType](id: Int): WidgetType = {
    findViewById(id).asInstanceOf[WidgetType]
  }

}

class ViewWithOnClick(view: View) {
  def onClick(action: View => Any) = {
    view.setOnClickListener(new View.OnClickListener() {
      def onClick(v: View) { action(v) }
    })
  }
}

object FindView extends Activity {
  implicit def addOnClickToViews(view: View) =
    new ViewWithOnClick(view)
}

有了以上的定义我们的原有的Activity就可以修改为

package org.noahx.scalaandroid

import android.app.Activity
import android.os.Bundle
import android.widget.Button
import android.widget.TextView
import android.view.View
import FindView._

class ScalaAndroidActivity extends Activity with FindView {

  lazy val text = findView[TextView](R.id.text1)
  lazy val button = findView[Button](R.id.button1)

  override protected def onCreate(savedInstanceState: Bundle) = {
    super.onCreate(savedInstanceState)

    setContentView(R.layout.main)

    button.onClick { view: View =>
      text.setText("hello scala!!!")
    }

  }

}

lazy方式也可以让组件定义全局化，便于使用

利用Scala语言的特点，代码变得简洁优雅