Kotlin implements a simple login page

technological process ： Enter login nickname + password , Click the login button , Login success displays success toast And enter Details page , Login failure displays failure toast

Kotlin Realize simple login page video

Source code ：

package com.example.kotlintest

import android.content.Intent
import android.os.Bundle
import android.text.Editable
import android.text.TextWatcher
import android.util.Log
import android.view.View
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*

/**
 * Created by tzbc on 2022/2/17.
 *  The login page 
 *
 * @author tzbc
 */
open class MainActivity : AppCompatActivity(), View.OnClickListener {

    companion object {
        const val TAG = "MainActivity"
        const val LEGAL_NAME = "tzbc"
        const val LEGAL_PSD = "123456"
        const val KEY_LOGIN_NAME = "KEY_LOGIN_NAME"
        const val KEY_LOGIN_PSD = "KEY_LOGIN_PSD"
    }

    // Initial name & Password noncompliance 
    private var nameLegal: Boolean = false
    private var psdLegal: Boolean = false

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

        initEditText()
        initClickListener()
    }


    private fun initEditText() {
        etLoginName.isFocusable = true
        etLoginName.addTextChangedListener(nameWatcher)
        etLoginPsd.addTextChangedListener(psdWatcher)
    }

    private fun initClickListener() {
        etLoginName.setOnClickListener(this)
        etLoginPsd.setOnClickListener(this)
        btGoLogin.setOnClickListener(this)
    }

    private val nameWatcher: TextWatcher = object : TextWatcher {
        override fun beforeTextChanged(s: CharSequence, start: Int, count: Int, after: Int) {}
        override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) {}

        override fun afterTextChanged(s: Editable) {
            // Get the current input 
            val input = s.toString()
            // Validation rules 
            Log.v(TAG, "nameWatcher_input=$input")
            nameLegal = input == LEGAL_NAME
            Log.v(TAG, "nameWatcher_nameLegal=$nameLegal")
        }
    }

    private val psdWatcher: TextWatcher = object : TextWatcher {
        override fun beforeTextChanged(s: CharSequence, start: Int, count: Int, after: Int) {}
        override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) {}

        override fun afterTextChanged(s: Editable) {
            // Get the current input 
            val input = s.toString()
            // Validation rules 
            Log.v(TAG, "psdWatcher_input=$input")
            psdLegal = input == LEGAL_PSD
            Log.v(TAG, "psdWatcher_psdLegal=$psdLegal")
        }
    }

    override fun onClick(v: View?) {
        if (v == null) {
            return
        }
        when (v.id) {
            R.id.btGoLogin -> {
                if (!nameLegal) {
                    Toast.makeText(this, "name illegal! Please retry.", Toast.LENGTH_SHORT).show()
                    return
                }
                if (!psdLegal) {
                    Toast.makeText(this, "password illegal! Please retry.", Toast.LENGTH_SHORT)
                        .show()
                    return
                }
                //name&psd All legal 
                Toast.makeText(this, "Login success!", Toast.LENGTH_SHORT).show()
                // Jump to login success page 
                val intent: Intent = Intent(this, LoginSuccessActivity::class.java)
                intent.putExtra(KEY_LOGIN_NAME, etLoginName.text.toString())
                intent.putExtra(KEY_LOGIN_PSD, etLoginPsd.text.toString())
                startActivity(intent)
            }
        }
    }

}

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:alpha="0.5"
        android:scaleType="centerCrop"
        android:src="@drawable/ee" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center_horizontal"
        android:orientation="vertical"
        android:paddingLeft="22dp"
        android:paddingRight="22dp">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="66dp"
            android:text="Welcome to join us!"
            android:textColor="#000000"
            android:textSize="26dp"
            android:textStyle="bold" />

        <EditText
            android:id="@+id/etLoginName"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="30dp"
            android:layout_marginTop="30dp"
            android:layout_marginRight="30dp"
            android:hint="Please input your name"
            android:textSize="18dp" />

        <EditText
            android:id="@+id/etLoginPsd"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="30dp"
            android:layout_marginTop="30dp"
            android:layout_marginRight="30dp"
            android:hint="Please input your password"
            android:textSize="18dp" />

        <Button
            android:id="@+id/btGoLogin"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="36dp"
            android:layout_marginTop="50dp"
            android:layout_marginRight="36dp"
            android:background="@drawable/sign_up_on_bg"
            android:paddingTop="14dp"
            android:paddingBottom="14dp"
            android:text="Go To Login"
            android:textColor="#ffffff"
            android:textSize="18dp" />

    </LinearLayout>
</FrameLayout>

package com.example.kotlintest

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import com.example.kotlintest.MainActivity.Companion.KEY_LOGIN_NAME
import com.example.kotlintest.MainActivity.Companion.KEY_LOGIN_PSD
import kotlinx.android.synthetic.main.activity_login_success.*

/**
 * Created by tzbc on 2022/2/17.
 *  Login success page 
 *
 * @author tzbc
 */
class LoginSuccessActivity : AppCompatActivity() {

    private var successName: String? = null
    private var successPsd: String? = null

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

        successName = intent.getStringExtra(KEY_LOGIN_NAME)
        successPsd = intent.getStringExtra(KEY_LOGIN_PSD)

        initLoginSuccessInfo()
    }

    private fun initLoginSuccessInfo() {
        tvLoginSuccessName?.text = successName ?: "Empty Name"
        tvLoginSuccessPsd?.text = successPsd ?: "Empty Psd"
    }
}

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:alpha="0.5"
        android:scaleType="centerCrop"
        android:src="@drawable/ee" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center_horizontal"
        android:orientation="vertical"
        android:paddingLeft="22dp"
        android:paddingRight="22dp">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="66dp"
            android:text="Welcome to join us!"
            android:textColor="#000000"
            android:textSize="26dp"
            android:textStyle="bold" />

        <TextView
            android:id="@+id/tvLoginSuccessName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="30dp"
            android:textColor="#000000"
            android:textSize="20dp" />

        <TextView
            android:id="@+id/tvLoginSuccessPsd"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:textColor="#000000"
            android:textSize="20dp" />

    </LinearLayout>
</FrameLayout>