记录问题Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW

博客详细记录了遇到的错误：Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK。原因是使用ApplicationContext启动Activity时，由于没有任务栈导致。解决方案是在启动Activity时添加FLAG_ACTIVITY_NEW_TASK标志。

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记录下该问题，自启动广播代码如下：

class BootBroadcastReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        if (intent.action == "android.intent.action.BOOT_COMPLETED") {
            val startupIntent = Intent(context, SplashActivity::class.java)
            
            context.startActivity(startupIntent)
        }
    }
}

然后报错：

java.lang.RuntimeException: Unable to start receiver ai.xmov.dualscreencanteen.service.BootBroadcastReceiver: android.util.AndroidRuntimeException: Calling startActivity() from outside of an Activity  context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?
06-18 10:39:33.431 E/AndroidRuntime( 1521): 	at android.app.ActivityThread.handleReceiver(ActivityThread.java:2636)
06-18 10:39:33.431 E/AndroidRuntime( 1521): 	at android.app.ActivityThread.access$1700(ActivityThread.java:151)
06-18 10:39:33.431 E/AndroidRuntime( 1521): 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1396)
06-18 10:39:33.431 E/AndroidRuntime( 1521): 	at android.os.Handler.dispatchMessage(Handler.java:102)
06-18 10:39:33.431 E/AndroidRuntime( 1521): 	at android.os.Looper.loop(Looper.java:135)
06-18 10:39:33.431 E/AndroidRuntime( 1521): 	at android.app.ActivityThread.main(ActivityThread.java:5280)
06-18 10:39:33.431 E/AndroidRuntime( 1521): 	at java.lang.reflect.Method.invoke(Native Method)
06-18 10:39:33.431 E/AndroidRuntime( 1521): 	at java.lang.reflect.Method.invoke(Method.java:372)
06-18 10:39:33.431 E/AndroidRuntime( 1521): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:963)
06-18 10:39:33.431 E/AndroidRuntime( 1521): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:758)

问题原因：

因为standard模式的Activity默认会进入启动它的Activity所属的任务栈中，但是由于非Activity类型的context（ApplicationContext）并没有所谓的任务栈，所以就出现问题了。需要指定Activity为FLAG_ACTIVITY_NEW_TASK标记位，这样启动的时候，就会为它创建一个新的任务栈了

解决代码：

class BootBroadcastReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        if (intent.action == "android.intent.action.BOOT_COMPLETED") {
            val startupIntent = Intent(context, SplashActivity::class.java)
            startupIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
            context.startActivity(startupIntent)
        }
    }
}