Android中NetworkStats.BucketquerySummaryForDevice中的空存储桶

如何解决Android中NetworkStats.BucketquerySummaryForDevice中的空存储桶

这是我的代码

                Calendar startCalendar;
                Calendar stopCalendar;
            startCalendar= Calendar.getInstance();
            stopCalendar=Calendar.getInstance();
            startCalendar.set(2020,10,2,0);
            stopCalendar.set(2020,3,0);
            networkstatsmanager networkstatsmanager = (networkstatsmanager) getContext().getSystemService(Context.NETWORK_STATS_SERVICE);
            NetworkStats.Bucket bucket;
                bucket = networkstatsmanager.querySummaryForDevice(NetworkStats.Bucket.DEFAULT_NETWORK_ALL,"",startCalendar.getTimeInMillis(),stopCalendar.getTimeInMillis());
                long rxBytes = bucket.getRxBytes();
                long txBytes = bucket.getTxBytes();

我想获取每天的互联网使用量。该应用程序需要使用数据，我还检查了清单中所需的权限。

这是日志

2020-10-02 10:42:56.448 28091-28091/com.sreejithsreejayan.internetspeedometer D/AndroidRuntime: Shutting down VM
2020-10-02 10:42:56.452 28091-28091/com.sreejithsreejayan.internetspeedometer E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.sreejithsreejayan.internetspeedometer,PID: 28091
    java.lang.NullPointerException: Attempt to invoke virtual method 'long android.app.usage.NetworkStats$Bucket.getRxBytes()' on a null object reference
        at com.sreejithsreejayan.internetspeedometer.ui.home.HomeFragment$2.onClick(HomeFragment.java:71)
        at android.view.View.performClick(View.java:7870)
        at android.widget.TextView.performClick(TextView.java:14970)
        at android.view.View.performClickInternal(View.java:7839)
        at android.view.View.access$3600(View.java:886)
        at android.view.View$PerformClick.run(View.java:29363)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:237)
        at android.app.ActivityThread.main(ActivityThread.java:7814)
        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:1068)
2020-10-02 10:42:56.490 28091-28091/com.sreejithsreejayan.internetspeedometer I/Process: Sending signal. PID: 28091 SIG: 9

为什么存储桶为空（空）。我是android开发的新手，请帮忙。

解决方法

我将NetworkStats.Bucket.DEFAULT_NETWORK_ALL替换为ConnectivityManager.TYPE_WIFI，但它不是null，但已弃用了ConnectivityManager.TYPE_WIFI