无法使用null启动服务[服务名称]

Question

我最近编写了一个Android Widget并在模拟器和我的Galaxy S上进行了测试,它在两者上都运行良好,在我发布到Android市场后,我现在收到一些错误报告.

我在Widget类的onUpdate中声明了一个服务,如下所示:

if (appWidgetIds != null) {
    final int N = appWidgetIds.length;

    // Perform this loop procedure for each App Widget that belongs to
    // this
    // provider
    for (int i = 0; i < N; i++) {
        // Start Service for each instance
        int appWidgetId = appWidgetIds[i];
        Intent active = new Intent(context, DialerService.class);
        active.setAction("Start");
        active.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID,
                appWidgetId);

        context.startService(active);
    }
}

有些人得到的错误是:

java.lang.RuntimeException: Unable to start service dialer.impact.DialerService@45f926f0 with null: java.lang.NullPointerException
at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:3282)
at android.app.ActivityThread.access$3600(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2211)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:144)
at android.app.ActivityThread.main(ActivityThread.java:4937)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
**at dialer.impact.DialerService.onStart(DialerService.java:18)**
at android.app.Service.onStartCommand(Service.java:420)
at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:3267)
... 10 more

错误说明NullPointerException第18行ServiceClass是这样的:

@Override
public void onStart(Intent intent, int startId) {
    //Line 18th 
            String command = intent.getAction();
    int appWidgetId = intent.getExtras().getInt(
            AppWidgetManager.EXTRA_APPWIDGET_ID);
    RemoteViews remoteView = new RemoteViews(getApplicationContext()
            .getPackageName(), R.layout.main);
    AppWidgetManager appWidgetManager = AppWidgetManager
            .getInstance(getApplicationContext());
}

第18行是 String command = intent.getAction();

什么可能是意图为null的原因请帮助

Answer 1

根据文档onStart()(实际上onStartCommand()但参数是相同的):

intent 提供给startService(Intent)的Intent,如给定的那样.如果服务在其进程消失后重新启动,则它可能为null,并且之前已返回除START_STICKY_COMPATIBILITY之外的任何内容.