从服务启动活动

Question

当我尝试从Service启动呼叫活动时，收到NullPointerException 。 这是我的代码：

Intent callIntent = new Intent(Intent.ACTION_CALL);
callIntent.setData(Uri.parse("tel:" + number));
callIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(callIntent);

我在startActivity行上遇到了异常。

我尝试使用getApplication.startActivity和getApplicationContext.startActivity但是没有运气。

有任何想法吗？

编辑 ：也许一些有用的信息：我正在尝试创建一个将在后台运行并扫描传感器数据的服务，当给出特定信号时，我想自动拨打一个号码。

编辑 ：完整的adb错误代码：

03-31 09:04:10.214: ERROR/AndroidRuntime(1896): Uncaught handler: thread main exiting due to uncaught exception
03-31 09:04:10.226: ERROR/AndroidRuntime(1896): java.lang.RuntimeException: Unable to instantiate service dfz.epilepsiedetector.services.DetectionService: java.lang.NullPointerException
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2668)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at android.app.ActivityThread.access$3100(ActivityThread.java:116)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1846)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at android.os.Looper.loop(Looper.java:123)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at android.app.ActivityThread.main(ActivityThread.java:4203)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at java.lang.reflect.Method.invokeNative(Native Method)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at java.lang.reflect.Method.invoke(Method.java:521)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at dalvik.system.NativeStart.main(Native Method)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896): Caused by: java.lang.NullPointerException
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at android.content.ContextWrapper.getPackageName(ContextWrapper.java:120)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at android.content.ComponentName.<init>(ComponentName.java:75)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at android.content.Intent.<init>(Intent.java:2302)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at dfz.epilepsiedetector.services.DetectionService.<init>(DetectionService.java:35)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at java.lang.Class.newInstanceImpl(Native Method)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at java.lang.Class.newInstance(Class.java:1472)
03-31 09:04:10.226: ERROR/AndroidRuntime(1896):     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2665)

编辑修剪的类代码：

public class DetectionService extends IntentService implements SensorEventListener
{   
 private SensorManager mSensorManager;
 private Sensor mAccelerometer;
 private boolean hasSeizure = false;

 private final int POLLS_PER_SECOND = 10;

 public DetectionService()
 {
 super("EpilepsionDetectionService");

 Intent callIntent = new Intent(DetectionService.this,
 InformationActivity.class);
 callIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);        
 getApplication().startActivity(callIntent);
}

Answer 1

您必须从调用服务的活动中获取上下文。

Intent callIntent = new Intent(Intent.ACTION_CALL);
callIntent.setData(Uri.parse("tel:" + number));


 callIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 context.startActivity(callIntent);

编辑 ：

callIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
getApplication().startActivity(callIntent);`

`

希望能帮助到你...

Answer 2

你可以试试：

getBaseContext().startActivity(callIntent);

或使用：

this.startActivity(callIntent);

Answer 3

备查：

当直接从Service而不是Intent服务中安装时，问题消失了。

希望对您有所帮助！

Answer 4

将代码移出构造函数，并移至onCreate()方法中。 总而言之，该类尚未完全初始化，并导致NullPointerException 。

Answer 5

在服务的onStart方法而不是onCreate方法中调用意图。