创建 Intent 结果 "Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()'"

Question

我正在尝试按照 Google 上的代码进行 creating a notification on Wear OS devices。

import androidx.core.app.NotificationCompat
import androidx.core.app.NotificationManagerCompat
import androidx.core.app.NotificationCompat.WearableExtender

class MainActivity : WearableActivity() {


    val notificationId = 1
    // The channel ID of the notification.
    val id = "my_channel_01"
    // Build intent for notification content
    val viewPendingIntent = Intent(this, com.alborz.innout.MainActivity::class.java).let { viewIntent ->
        viewIntent.putExtra(EXTRA_EVENT_ID, notificationId)
        PendingIntent.getActivity(this, 0, viewIntent, 0)
    }
    // Notification channel ID is ignored for Android 7.1.1
    // (API level 25) and lower.
    val notificationBuilder = NotificationCompat.Builder(this, id)
        .setLocalOnly(true)
        .setSmallIcon(R.drawable.ic_launcher_foreground)
        .setContentTitle("TITLE")
        .setContentText("TEXT")
        .setContentIntent(viewPendingIntent)

稍后我尝试激活通知，如下所示：

    button_in.setOnClickListener {
        NotificationManagerCompat.from(this).apply {
            notify(notificationId, notificationBuilder.build())
        }
    }

但是我收到一个我不明白的错误。（我是 Kotlin 的超级新手，所以可能错过了一些明显的东西）

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.alb.innout/com.alb.innout.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2844)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3049)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1809)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6680)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
        at android.content.ContextWrapper.getPackageName(ContextWrapper.java:142)
        at android.content.ComponentName.<init>(ComponentName.java:130)
        at android.content.Intent.<init>(Intent.java:6082)
        at com.alb.innout.MainActivity.<init>(MainActivity.kt:46)

第 46 行是 val viewPendingIntent = Intent ...

Answer 1

您应该将此 Intent 和通知设置放在一个函数中，并在发送通知时调用该函数。按照你现在的方式，Intent 是在实例化 Activity 时创建的，这是在 onCreate() 之前，而且对于它作为函数的 this 参数传递来说还为时过早和想要使用其上下文的构造函数。

创建 Intent 结果 "Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()'"

Creating Intent results in "Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()'"

kotlin

android-notifications

wear-os