焦点改变事件OnFocusChangeListener

效果图

1.MainActivity.java

 package com.example.app2;

 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.view.View;
 import android.widget.EditText;
 import android.widget.TextView;

 public class MainActivity extends AppCompatActivity {
     private TextView textView;
     private EditText editText;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         textView = (TextView) findViewById(R.id.tv_show);
         editText = (EditText) findViewById(R.id.et_mail1);

         editText.setOnFocusChangeListener(new View.OnFocusChangeListener() {
             @Override
             public void onFocusChange(View v, boolean hasFocus) {
                 String et_info = editText.getText().toString();
                 String reges="\\w+@\\w+(\\.\\w{2,3})*\\.\\w{2,3}";      //正则表达式验证邮箱是否正确
                 if(et_info.matches(reges)){
                     textView.setText("您输入的邮箱是："+et_info+"符合条件");
                 }else{
                     textView.setText("您输入的邮箱是："+et_info+"不符合条件");
                 }
             }
         });

     }
 }

2.activity_main.xml

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:paddingBottom="@dimen/activity_vertical_margin"
     android:paddingLeft="@dimen/activity_horizontal_margin"
     android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin"
     tools:context="com.example.app2.MainActivity"
     android:orientation="vertical"
     >

     <TextView
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="请输入您的邮箱" />
     <EditText
         android:id="@+id/et_mail1"
         android:hint="第一个文本输入框"
         android:layout_width="match_parent"
         android:layout_height="wrap_content" />
     <EditText
         android:id="@+id/et_mail2"
         android:hint="第二个文本输入框"
         android:layout_width="match_parent"
         android:layout_height="wrap_content" />
     <TextView
         android:id="@+id/tv_show"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content" />
 </LinearLayout>