问当您尝试启动应用程序时，它将关闭

EN

    package com.makar_mikhalchenko.itchat;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.TextView;

import com.firebase.ui.auth.AuthUI;
import com.firebase.ui.database.FirebaseListAdapter;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.FirebaseDatabase;

import android.text.format.DateFormat;

import java.util.Objects;

public class MainActivity extends AppCompatActivity {

    private static int SIGN_IN_CODE = 1;
    private RelativeLayout activity_main;
    private FirebaseListAdapter<Message> adapter;
    private FloatingActionButton sendBtn;

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode == SIGN_IN_CODE){
            if (resultCode == RESULT_OK){
                Snackbar.make(activity_main, "Вы авторизованы", Snackbar.LENGTH_LONG).show();
                displayAllMessages();
            }else{
                Snackbar.make(activity_main, "Вы не авторизованы", Snackbar.LENGTH_LONG).show();
                finish();
            }
        }
    }

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

        activity_main = findViewById(R.id.activity_main);
        sendBtn = findViewById(R.id.btnSend);
        sendBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                EditText textField = findViewById(R.id.messageField);
                if (textField.getText().toString() == "")
                    return;
                FirebaseDatabase.getInstance().getReference().push().setValue(
                        new Message(FirebaseAuth.getInstance().getCurrentUser().getEmail(), textField.getText().toString()));
                textField.setText("");
            }

        });

        //пользователь ещё не авторизован
        if (FirebaseAuth.getInstance().getCurrentUser() == null)
            startActivityForResult(AuthUI.getInstance().createSignInIntentBuilder().build(), SIGN_IN_CODE);
        else {
            Snackbar.make(activity_main, "Вы авторизованы", Snackbar.LENGTH_LONG).show();

            displayAllMessages();
        }
    }

    private void displayAllMessages() {
        ListView listOfMessages = findViewById(R.id.list_of_messages);
        adapter = new FirebaseListAdapter<Message>(this, Message.class, R.layout.list_item, FirebaseDatabase.getInstance().getReference()) {
            @Override
            protected void populateView(View v, Message model, int position) {
                TextView mess_user, mess_time, mess_text;
                mess_user = v.findViewById(R.id.message_user);
                mess_time = v.findViewById(R.id.message_time);
                mess_text = v.findViewById(R.id.message_text);

                mess_user.setText(model.getUserName());
                mess_text.setText(model.getTextMessage());
                mess_time.setText(DateFormat.format("dd-mm-yy HH:mm:ss", model.getMessageTime()));
            }
        };

        listOfMessages.setAdapter(adapter);
    }
}

    <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity"
        android:id="@+id/activity_main">
    
        <com.google.android.material.floatingactionbutton.FloatingActionButton
            android:id="@+id/btnSend"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:clickable="true"
            android:src="@drawable/ic_send_button"
            android:tint="@android:color/white"
            android:layout_alignParentBottom="true"
            android:layout_alignParentEnd="true"
            android:layout_marginRight="5sp"
            android:layout_marginBottom="5sp"
    
            />
    
        <com.google.android.material.textfield.TextInputLayout
            android:id="@+id/text_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_alignParentStart="true"
            android:layout_toLeftOf="@+id/btnSend">
    
            <EditText
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/messageField"
                android:hint="Введите сообщение"
                />
    
        </com.google.android.material.textfield.TextInputLayout>
    
        <ListView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_above="@+id/text_layout"
            android:id="@+id/list_of_messages"
            android:layout_alignParentTop="true"
            android:layout_alignParentStart="true"
            android:divider="@android:color/transparent"
            android:dividerHeight="16dp"
            android:layout_marginBottom="12dp"
    
            >
    
        </ListView>
    </RelativeLayout>

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.makar_mikhalchenko.itchat, PID: 8987
    java.lang.NoClassDefFoundError: Failed resolution of: Lcom/google/android/gms/common/api/Api$zzf;
        at com.google.android.gms.auth.api.Auth.<clinit>(Unknown Source)
        at com.firebase.ui.auth.util.CredentialsAPI.initGoogleApiClient(CredentialsAPI.java:145)
        at com.firebase.ui.auth.util.CredentialsAPI.<init>(CredentialsAPI.java:65)
        at com.firebase.ui.auth.ui.ChooseAccountActivity.onCreate(ChooseAccountActivity.java:91)
        at android.app.Activity.performCreate(Activity.java:6679)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
        at android.app.ActivityThread.-wrap12(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6119)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
     Caused by: java.lang.ClassNotFoundException: Didn't find class "com.google.android.gms.common.api.Api$zzf" on path: DexPathList[[zip file "/data/app/com.makar_mikhalchenko.itchat-1/base.apk"],nativeLibraryDirectories=[/data/app/com.makar_mikhalchenko.itchat-1/lib/x86, /system/lib, /vendor/lib]]
        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:380)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
        at com.google.android.gms.auth.api.Auth.<clinit>(Unknown Source) 
        at com.firebase.ui.auth.util.CredentialsAPI.initGoogleApiClient(CredentialsAPI.java:145) 
        at com.firebase.ui.auth.util.CredentialsAPI.<init>(CredentialsAPI.java:65) 
        at com.firebase.ui.auth.ui.ChooseAccountActivity.onCreate(ChooseAccountActivity.java:91) 
        at android.app.Activity.performCreate(Activity.java:6679) 
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) 
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
        at android.app.ActivityThread.-wrap12(ActivityThread.java) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6119) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
I/FA: Tag Manager is not found and thus will not be used
D/FA: Logging event (FE): screen_view(_vs), Bundle[{firebase_event_origin(_o)=auto, firebase_screen_class(_sc)=MainActivity, firebase_screen_id(_si)=-2868454111777039973}]
V/FA: Connection attempt already in progress
V/FA: Connection attempt already in progress
    Activity resumed, time: 2583628
V/FA: Screen exposed for less than 1000 ms. Event not sent. time: 444
V/FA: Connection attempt already in progress
    Activity paused, time: 2583641

apply plugin: 'com.android.application'

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.2"

    defaultConfig {
        applicationId "com.makar_mikhalchenko.itchat"
        minSdkVersion 24
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}


dependencies {
    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.1'
    implementation 'com.google.android.material:material:1.2.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
    implementation 'com.google.firebase:firebase-analytics:17.5.0'
    implementation 'com.google.android.material:material:1.2.0'
    implementation 'com.google.firebase:firebase-auth:19.3.2'
    implementation 'com.google.firebase:firebase-database:19.4.0'
    implementation 'com.firebaseui:firebase-ui:0.6.2'
    implementation 'com.google.android.gms:play-services-auth:18.1.0'

}

//apply plugin: 'com.google.gms.google-services'