LiveData_LifecycleBoundObserver_LifecycleAdapter无法强制转换为GeneratedAdapter

Question

我在我的android工作室项目中使用kotlin，我正在尝试将一个观察者添加到包含MutableLiveData的ArrayList，但我在下面得到了例外。

java.lang.ClassCastException: android.arch.lifecycle.LiveData_LifecycleBoundObserver_LifecycleAdapter cannot be cast to android.arch.lifecycle.GeneratedAdapt
    at android.arch.lifecycle.Lifecycling.createGeneratedAdapter(Lifecycling.java:79)
    at android.arch.lifecycle.Lifecycling.getCallback(Lifecycling.java:62)
    at android.arch.lifecycle.LifecycleRegistry$ObserverWithState.<init>(LifecycleRegistry.java:346)
    at android.arch.lifecycle.LifecycleRegistry.addObserver(LifecycleRegistry.java:162)
    at android.arch.lifecycle.LiveData.observe(LiveData.java:199)

项目级build.gradle

buildscript {
    ext.kotlin_version = '1.2.10'
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.0-alpha05'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

app的build.gradle

android {      
    dataBinding {
        enabled true;
    }
}
dependencies {
    implementation "android.arch.lifecycle:runtime:1.0.3"
    implementation "android.arch.lifecycle:extensions:1.0.0-alpha9-1"
    kapt "android.arch.lifecycle:compiler:1.0.0-alpha9-1"
//...
}

我的活动

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    //...
    val liveData = MutableLiveData<ArrayList<Media>>()
    //...
    liveData.observe(this, object : Observer<ArrayList<Media>>{
            override fun onChanged(t: ArrayList<Media>?) {
                if(t?.size!! > 0){
                    binding.totalTv.text =t.size.toString()
                    binding.totalTv.visibility = View.VISIBLE
                }
            }
    })
    //...
}

我该如何解决错误？

Answer 1

我改变了android.arch.lifecycle:extensions

从

 implementation "android.arch.lifecycle:extensions:1.0.0-alpha9-1"

至

implementation "android.arch.lifecycle:extensions:1.0.0"

然后同步我的项目，它成功了。感谢@MatPag的洞察力

Answer 2

我用以下代码测试了你的代码：

• dataBinding {
      enabled true
  }

• sourceCompatibility和targetCompatibility到Java 8
• gradle 4.2.1
• android plugin 3.0.1
• kotlin plugin 1.2.10

依赖关系：

• appcompat-v7 27.0.2
• android.arch.lifecycle:runtime:1.0.3
• android.arch.lifecycle:extensions:1.0.0
• android.arch.lifecycle:compiler:1.0.0

一切都很好......