我正在尝试连接到Android Studio 3.2.1中的firebase。应用implementation 'com.google.firebase:firebase-database:16.0.1:15.0.0'之后，firebase依赖关系已正确设置，并且在我删除15.0.0时，firebase依赖关系已断开连接。同样，当连接到手机（Android版本7.1.1，系统版本26.31.1）时，应用也会崩溃。
我该如何进行？
apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support:customtabs:27.1.1'
implementation 'com.android.support:support-media-compat:27.1.1'
implementation 'com.android.support:support-v4:27.1.1'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
implementation 'com.google.firebase:firebase-core:16.0.4'
implementation 'com.google.firebase:firebase-database:16.0.3'
implementation 'com.google.android.gms:play-services-ads:17.0.0'
implementation 'com.google.android.gms:play-services-auth:16.0.1'
implementation 'com.google.firebase:firebase-messaging:17.3.4'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
implementation 'com.google.android.gms:play-services-maps:16.0.0'
implementation 'com.google.firebase:firebase-database:16.0.2'
implementation 'com.google.firebase:firebase-database:16.0.1'
implementation 'com.google.firebase:firebase-database:16.0.1:15.0.0'