Wear OS - 使用片段设置项目

Question

我正在尝试建立一个 Wear OS 项目。我有一些正常 android 开发的经验，但 Wear os 对我来说是新的。

我习惯了只有一个 MainActivity 和一些片段。但我正试图让 Wear OS 工作，但没有成功。当我想在 OverviewFragment.kt.

中使用 viewBinding 时，它一直崩溃

我现在得到了以下项目：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.wear.widget.BoxInsetLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="@dimen/box_inset_layout_padding"
    tools:context=".MainActivity"
    tools:deviceIds="wear">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="@dimen/inner_frame_layout_padding"
        app:layout_boxedEdges="left|right">

        <include
            layout="@layout/content_main"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </FrameLayout>
</androidx.wear.widget.BoxInsetLayout>

content_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.wear.widget.BoxInsetLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior">

    <fragment
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/nav_graph" />
</androidx.wear.widget.BoxInsetLayout>

fragment_overview.xml

<?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"
    tools:context=".ui.OverviewFragment">

    <TextView
        android:id="@+id/tvOverview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:clickable="true"
        android:text="overview"
        android:textAlignment="center" />

</FrameLayout>

MainActivity.kt

class MainActivity : FragmentActivity() {

    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)
    }
}

OverviewFragment.kt

class OverviewFragment : Fragment() {

    private var _binding: FragmentOverviewBinding? = null
    private val binding get() = _binding!!

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_overview, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        binding.tvOverview.setOnClickListener {
            println("great")
        }
    }
}

只是一个简单的设计，但不像OverviewFragment.kt中的binding.tvOverview.setOnClickListener部分。它一直在崩溃。

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.krakert.tracker, PID: 7261
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.krakert.tracker/com.krakert.tracker.MainActivity}: android.view.InflateException: Binary XML file line #17: Binary XML file line #8: Error inflating class fragment
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
     Caused by: android.view.InflateException: Binary XML file line #17: Binary XML file line #8: Error inflating class fragment
     Caused by: android.view.InflateException: Binary XML file line #8: Error inflating class fragment
     Caused by: java.lang.NullPointerException
        at com.krakert.tracker.ui.OverviewFragment.getBinding(OverviewFragment.kt:15)
        at com.krakert.tracker.ui.OverviewFragment.onViewCreated(OverviewFragment.kt:28)

我需要一些帮助，设置项目。真的很新 Wear OS

谢谢！

Answer 1

不确定这是如何工作的，怀疑这是 NullPointerException 的来源

    private var _binding: FragmentOverviewBinding? = null
    private val binding get() = _binding!!

与 https://developer.android.com/topic/libraries/view-binding#fragments

中的示例进行比较

在 onCreateView

中设置 _binding

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