Android最简单的限制输入方法（只包含数字、字母和符号）

class LimitEditText(context: Context, attrs: AttributeSet, defStyleAttr: Int)
 : EditText(context, attrs, defStyleAttr) {

 constructor(context: Context, attrs: AttributeSet) : this(context, attrs, 0)

 /**
  * 输入法
  */
 override fun onCreateInputConnection(outAttrs: EditorInfo?): InputConnection {
  return InnerInputConnection(super.onCreateInputConnection(outAttrs), false)
 }

}

class InnerInputConnection(target: InputConnection, mutable: Boolean)
 : InputConnectionWrapper(target, mutable) {
 // 数字,字母
 private val pattern = Pattern.compile("^[0-9A-Za-z_]\$")
 // 标点
 private val patternChar = Pattern.compile("[^\\w\\s]+")
 // EmoJi
 private val patternEmoJi = Pattern.compile("[\ud83c\udc00-\ud83c\udfff]|[\ud83d\udc00-\ud83d\udfff]|[\u2600-\u27ff]", Pattern.UNICODE_CASE or Pattern.CASE_INSENSITIVE)
 // 英文标点
 private val patternEn = Pattern.compile("^[`~!@#\$%^&*()_\\-+=<>?:\"{},.\\\\/;'\\[\\]]\$")
 // 中文标点
 private val patternCn = Pattern.compile("^[·！#￥（——）：；“”‘、，|《。》？、【】\\[\\]]\$")


 // 对输入拦截
 override fun commitText(text: CharSequence?, newCursorPosition: Int): Boolean {
  if (patternEmoJi.matcher(text).find()){
   return false
  }

  if (pattern.matcher(text).matches() || patternChar.matcher(text).matches()) {
   return super.commitText(text, newCursorPosition)
  }
  return false
 }

}

<?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"
 tools:context="cn.molue.jooyer.limitedittext.MainActivity">

 <cn.molue.jooyer.limitedittext.LimitEditText
  android:id="@+id/let_main"
  android:layout_width="match_parent"
  android:layout_height="50dp"
  android:layout_margin="10dp"
  android:text="Hello World!"
  app:layout_constraintLeft_toLeftOf="parent"
  app:layout_constraintRight_toRightOf="parent"
  app:layout_constraintTop_toTopOf="parent"/>

</android.support.constraint.ConstraintLayout>

class MainActivity : AppCompatActivity() {

 override fun onCreate(savedInstanceState: Bundle?) {
  super.onCreate(savedInstanceState)
  setContentView(R.layout.activity_main)

  // demo 中默认 LimitEditText 只能输入字母数字和标点符号

  // 延时主要是更方便观察
  window.decorView.postDelayed({
   // 注意,获得焦点需要自己再处理下,其实很简单,如下:
   let_main.isFocusable = true
   let_main.isFocusableInTouchMode = true
   let_main.requestFocus()

  },1000)
 }
}