Kotlin Android按钮

Android Button是用于在单击时执行事件的按钮。它是android.widget.Button类下的一个UI组件。要了解有关Android Button的更多信息, 请参阅Android Button示例

使用Kotlin, 我们可以使用以下方法通过不同的方式在Android Button上执行事件：

1.实现Button的setOnClickListener

button1.setOnClickListener(){
            Toast.makeText(this, "button 1 clicked", Toast.LENGTH_SHORT).show()
        }

2.实现View.OnClickListner并覆盖其功能

button2.setOnClickListener(this) 
    . .
    override fun onClick(view: View) {
        //  TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    }

3.在布局文件中添加Button的onClick属性并实现其功能。

<Button
                android:onClick="clickButton"/>

    fun clickButton(v: View){
        val mToast = Toast.makeText(applicationContext, "button 3 clicked", Toast.LENGTH_SHORT)
        mToast.show()
    }

4.以编程方式创建一个Button并将其设置在布局上

button4.setLayoutParams(ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT))
        button4.setId(button4_Id)
        button4.x = 250f
        button4.y = 500f
        button4.setOnClickListener(this)
        constraintLayout.addView(button4)

Kotlin Android按钮示例

在此示例中, 我们将创建Button并对其执行事件。单击按钮, 显示一条祝酒消息。

activity_main.xml

在activity_main.xml布局文件中的Widgets面板中添加三个Button。其代码如下。 id button3的Button添加了onClick属性, 其函数名称在MainActivity类文件中实现。

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/constraintLayout"
    tools:context="example.srcmini02.com.kotlinbutton.MainActivity">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button Action Example"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.073"
        android:textAppearance="@style/Base.TextAppearance.AppCompat.Medium"/>

    <Button
        android:id="@+id/button1"
        android:layout_width="95dp"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Button 1"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.501"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.498" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="80dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Button 2"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.762" />

    <Button
        android:id="@+id/button3"
        android:layout_width="101dp"
        android:layout_height="48dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:onClick="clickButton"
        android:text="Button 3"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.502"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.774" />
</android.support.constraint.ConstraintLayout>

MainActivity.kt

在MainActivity.kt类中添加以下代码。在此类中, 我们在按钮上实现setOnClickListener侦听器, 实现View类（View.OnClickListener）的OnClickListener并覆盖其功能onClick。在该类中, 我们还以编程方式创建一个Button（button4）, 定义其属性并将其设置在布局上。

package example.srcmini02.com.kotlinbutton

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() , View.OnClickListener {
    val button4_Id: Int = 1111
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        button1.setOnClickListener(){
            Toast.makeText(this, "button 1 clicked", Toast.LENGTH_SHORT).show()
        }
        button2.setOnClickListener(this)
        // add button dynamically
        val button4 = Button(this)
        button4.setText("Button 4 added dynamically")
        button4.setLayoutParams(ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT))
        button4.setId(button4_Id)
        button4.x = 250f
        button4.y = 500f
        button4.setOnClickListener(this)
        constraintLayout.addView(button4)
    }
    override fun onClick(view: View) {
        //  TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
        when (view.id) {
            R.id.button2 ->
                Toast.makeText(this, "button 2 clicked", Toast.LENGTH_SHORT).show()//single line code
            button4_Id->{//multiline code
                val myToast = Toast.makeText(this, "button 4 clicked", Toast.LENGTH_SHORT)
                myToast.show()
            }
        }
    }
    fun clickButton(v: View){
        val mToast = Toast.makeText(applicationContext, "button 3 clicked", Toast.LENGTH_SHORT)
        mToast.show()
    }
}

输出：