NetworkStats.Bucket (querySummaryForDevice) Android中存储桶为空

Question

这是我的代码

                Calendar startCalendar;
                Calendar stopCalendar;
            startCalendar= Calendar.getInstance();
            stopCalendar=Calendar.getInstance();
            startCalendar.set(2020,10,2,0,0);
            stopCalendar.set(2020,10,3,0,0);
            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();

我想知道每天的网络使用量。应用程序可以访问数据使用，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(Null)。我是android开发的新手，请帮助我。

Answer 1

我用ConnectivityManager.TYPE_WIFI替换了NetworkStats.Bucket.DEFAULT_NETWORK_ALL，但它不是空的，但ConnectivityManager.TYPE_WIFI已弃用