AlertDialog 的介绍

1. AlertDialog的方法

2. AlertDialog的创建

AlertDialog的构造函数都是protected的，因此我们无法直接通过构造函数实例化，所以SDK提供了 AlertDialog.Builder这个内部类用来创建AlertDialog

//Theme.AppCompat.Dialog主题常用的一般有以下属性：
<!-- 背景透明 -->  
<item name="android:windowBackground">@android:color/transparent</item>  
<!-- 边框 -->  
<item name="android:windowFrame">@null</item>  
<!-- 是否浮现在activity之上 -->  
<item name="android:windowIsFloating">true</item>  
<!-- 是否半透明 -->  
<item name="android:windowIsTranslucent">true</item>  
<!-- 是否无标题 -->  
<item name="android:windowNoTitle">true</item>  
<!-- Dialog背景样式 --> 
<item name="android:background">@android:color/transparent</item>  
<!-- 模糊 -->  
<item name="android:backgroundDimEnabled">true</item>  
<!-- 遮罩层 -->  
<item name="android:backgroundDimAmount">0.5</item> 
<!-- Dialog的宽度和屏幕的比例 -->  
<item name="android:windowMinWidthMinor">80%</item>
<!-- Dialog的最小宽度 -->  
<item name="android:minWidth">300dp</item>
<!-- Dialog的最小高度 -->  
<item name="android:minHeight">200dp</item>

AlertDialog 的使用

1.提示对话框

val builder = AlertDialog.Builder(this)
builder.setTitle("Title")
builder.setMessage("Message")
//设置Neutral按钮（最左边的按钮）
builder.setNeutralButton("Neutral") { _, _ ->
    Toast.makeText(
        this@MainActivity,
        "点击了Neutral",
        Toast.LENGTH_SHORT
    ).show()
}
//设置Positive按钮
builder.setPositiveButton("Positive") { _, _ ->
    Toast.makeText(
        this@MainActivity,
        "点击了Positive",
        Toast.LENGTH_SHORT
    ).show()
}
//设置Negative按钮
builder.setNegativeButton("Negative") { _, _ ->
    Toast.makeText(
        this@MainActivity,
        "点击了Negative",
        Toast.LENGTH_SHORT
    ).show()
}
//设置在对话框因任何原因关闭时将调用的回调。
builder.setOnDismissListener {
    Toast.makeText(
        this@MainActivity,
        "对话框Dismiss了",
        Toast.LENGTH_SHORT
    ).show()
}
//设置在对话框取消时将调用的回调
//        builder.setOnCancelListener {
//            Toast.makeText(
//                this@MainActivity,
//                "对话框Cancel了",
//                Toast.LENGTH_SHORT
//            ).show()
//        }
//点击对话框以外的区域是否让对话框消失，默认为true；
builder.setCancelable(false)

//设置对话框的title左边的图标；
builder.setIcon(resources.getDrawable(R.drawable.ic_launcher_background,null))

val dialog = builder.create()
//这个是Dialog中的方法，builder中没有这个方法
dialog.setOnShowListener {
    Toast.makeText(
        this@MainActivity,
        "对话框Show了",
        Toast.LENGTH_SHORT
    ).show()
}
dialog.show()

截屏2021-09-01 上午9.44.28.png

2. 列表对话框

   val builder = AlertDialog.Builder(this)
   builder.setCancelable(false)
   builder.setTitle("这是ListDialog")
   builder.setIcon(R.mipmap.ic_launcher)
   builder.setNegativeButton("取消") { _, _ ->
     Toast.makeText(
         this@MainActivity,
         "点击取消",
         Toast.LENGTH_SHORT
     ).show()
   }
   
   builder.setPositiveButton("确定") { _, _ ->
     Toast.makeText(
         this@MainActivity,
         "点击确定",
         Toast.LENGTH_SHORT
     ).show()
   }
   val list = arrayOf("语文", "数学", "英语", "化学", "生物", "物理", "体育")
   //设置列表
   builder.setItems(list) { p0, p1 ->
     Toast.makeText(
         this@MainActivity,
         "点击了第${p1}行",
         Toast.LENGTH_SHORT
     ).show()
   }
   builder.create().show()
   

截屏2021-09-01 上午10.12.04.png

3. 单选对话框

   val builder = AlertDialog.Builder(this)
   builder.setCancelable(false)
   builder.setTitle("这是ListDialog")
   builder.setIcon(R.mipmap.ic_launcher)
   builder.setNegativeButton("取消") { _, _ ->
       Toast.makeText(
           this@MainActivity,
           "点击取消",
           Toast.LENGTH_SHORT
       ).show()
   }
   
   builder.setPositiveButton("确定") { _, _ ->
       Toast.makeText(
           this@MainActivity,
           "点击确定",
           Toast.LENGTH_SHORT
       ).show()
   }
   val list = arrayOf("语文", "数学", "英语", "化学", "生物", "物理", "体育")
   //设置列表
   
   builder.setSingleChoiceItems(list,3) { p0, p1 ->
       Toast.makeText(
           this@MainActivity,
           "点击了第${p1}行",
           Toast.LENGTH_SHORT
       ).show()
   }
   builder.create().show()
   

截屏2021-09-01 上午10.15.53.png

4. 多选对话框

   val builder = AlertDialog.Builder(this)
           builder.setCancelable(false)
           builder.setTitle("这是ListDialog")
           builder.setIcon(R.mipmap.ic_launcher)
           builder.setNegativeButton("取消") { _, _ ->
               Toast.makeText(
                   this@MainActivity,
                   "点击取消",
                   Toast.LENGTH_SHORT
               ).show()
           }
   
           builder.setPositiveButton("确定") { _, _ ->
               Toast.makeText(
                   this@MainActivity,
                   "点击确定",
                   Toast.LENGTH_SHORT
               ).show()
           }
           val list = arrayOf("语文", "数学", "英语", "化学", "生物", "物理", "体育")
           var checked = booleanArrayOf(false,false,true,false,false,true,false)
           //设置列表
           builder.setMultiChoiceItems(list,checked
           ) { _, p1, p2 ->
               Toast.makeText(
                   this@MainActivity,
                   "点击了第${p1}行 $p2",
                   Toast.LENGTH_SHORT
               ).show()
           }
           builder.create().show()
   

截屏2021-09-01 上午10.29.13.png

5. 自定义弹窗

    val builder = AlertDialog.Builder(this, R.style.CustomDialog)
        builder.setCancelable(true)
        val view = layoutInflater.inflate(R.layout.custom_layout, null, false)
        val binding = CustomLayoutBinding.bind(view)
   
        builder.setView(view)
        val dialog =  builder.create()
        dialog.show()
   
        binding.cancelButton.setOnClickListener {
            Toast.makeText(
                this@MainActivity,
                "点击了取消",
                Toast.LENGTH_SHORT
            ).show()
            dialog.dismiss()
        }
        binding.okButton.setOnClickListener {
            Toast.makeText(
                this@MainActivity,
                "点击了确认",
                Toast.LENGTH_SHORT
            ).show()
        }
   

   custom_layout.xml

   <?xml version="1.0" encoding="utf-8"?>
   <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:app="http://schemas.android.com/apk/res-auto"
       android:layout_width="match_parent"
       android:layout_height="match_parent">
   
   
       <Button
           android:id="@+id/cancel_button"
           android:layout_width="100dp"
           android:layout_height="50dp"
           android:layout_marginLeft="40dp"
           android:backgroundTint="#f00"
           android:text="取消"
           android:textColor="#0f0"
           android:textSize="20sp"
           app:layout_constraintBottom_toBottomOf="parent"
           app:layout_constraintStart_toStartOf="parent" />
   
       <Button
           android:id="@+id/ok_button"
           android:layout_width="100dp"
           android:layout_height="50dp"
           android:layout_marginRight="40dp"
           android:backgroundTint="#0f0"
           android:text="确定"
           android:textColor="#f00"
           android:textSize="20sp"
           app:layout_constraintBottom_toBottomOf="parent"
           app:layout_constraintEnd_toEndOf="parent" />
   
       <TextView
           android:id="@+id/message"
           android:layout_width="wrap_content"
           android:layout_height="80dp"
           android:layout_marginTop="60dp"
           android:gravity="center"
           android:text="Message"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="@id/title"
           app:layout_constraintBottom_toTopOf="@id/cancel_button"
           />
   
       <TextView
           android:id="@+id/title"
           android:layout_width="0dp"
           android:layout_height="30dp"
           android:layout_marginLeft="30dp"
           android:layout_marginRight="30dp"
           android:gravity="center"
           android:text="标题"
           app:layout_constraintBottom_toTopOf="@id/message"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintTop_toTopOf="parent" />
   
   
   </androidx.constraintlayout.widget.ConstraintLayout>
   

   截屏2021-09-01 下午12.09.12.png

   如何修改Dialog的宽度和高度

   直接在layout.xml修改layout_width和layout_height是无法修改Dialog的宽和高的需要自定义一个theme，使用这个theme创建AlertDialog.

     <style name="CustomDialog" parent="Theme.AppCompat.Dialog">
           <!-- dialog  宽度与屏幕比例-->
           <!--        <item name="android:windowMinWidthMinor">80%</item>-->
           <!--设置最小宽度-->
           <item name="android:minWidth">300dp</item>
           <!--设置最小高度-->
           <item name="android:minHeight">200dp</item>
       </style>
   

   通过代码修改AlertDialog的大小

   //这段代码必须放在show()方法之后，否则没有作用
   dialog.window?.setLayout(100,200)
   

   如何修改AlertDialog的位置

   //这段代码必须放在show()方法之前，否则没有作用 当x,y都为0则居中显示
   val para = dialog.window?.attributes
   para?.x = 100 
   para?.y = 100