Question

我试图提供一项服务来识别用户的当前活动。但是此代码每次都会崩溃。

它引发异常：

java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'com.google.android.gms.location.DetectedActivity com.google.android.gms.location.ActivityRecognitionResult.getMostProbableActivity（）' 在com.always_in_beta.ecodrive.service.UserTrackService.detectActivity（UserTrackService.java:51）在com.always_in_beta.ecodrive.service.UserTrackService $ 1.run（UserTrackService.java:27）

代码是：

public class UserTrackService extends Service {

    public Handler handler = null;
    public Runnable runnable = null;
    int count = 0;
    public Context context = this;
    public Intent intentt;

    @Override
    public void onCreate() {
        handler = new Handler();
        runnable = new Runnable() {
            public void run() {
                detectActivity();
            }
        };
        handler.postDelayed(runnable, 4000);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        Toast.makeText(context, "Service stopped", Toast.LENGTH_LONG).show();
    }

    @Override
    public IBinder onBind(Intent intent) {
        intentt = intent;
        return null;
    }

    public void detectActivity() {
        ActivityRecognitionResult result = ActivityRecognitionResult.extractResult(intentt);
        DetectedActivity activity = result.getMostProbableActivity();
        Toast.makeText(context, activity.toString(), Toast.LENGTH_SHORT).show();
        Log.d("tag_tag_tag", activity.toString());
    }
}

Answer 1

ActivityRecognitionResult#extractResult(android.content.Intent)

返回 ActivityRecognitionResult，如果意图不成立，则为null 包含一个ActivityRecognitionResult。

因此，根据您的空指针堆栈跟踪，这是预料之中的，因为您无法在 null 上运行getMostProbableActivity()。

如何从服务中识别用户的当前活动？

1 个答案: