我的应用程序崩溃时,我注册一个传感器监听器 [英] My Application Crashes when I Register a Sensor Listener
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问题描述
在Android的我创建一个服务,该服务将监听传感器值的变化。
但是,我的应用程序总是崩溃,每当我打开它。如果我删除线
In Android I am creating a Service, which will listen for sensor value change. But my application keeps crashing whenever I open it. If I remove the Lines
sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
mAccelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
sensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
它正常工作
我已经创建了服务类如下:
I have created the Service class as following:
public class CustomSensorService extends Service implements SensorEventListener{
static SensorManager sensorManager;
static Sensor mAccelerometer;
static Context mContext;
static final String LOG_TAG = "SimpleService";
@Override
public void onCreate() {
super.onCreate();
Toast.makeText(this,"Service Created",Toast.LENGTH_SHORT).show();
sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
mAccelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
sensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
}
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}
@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
// TODO Auto-generated method stub
}
@Override
public void onSensorChanged(SensorEvent event) {
Log.d( LOG_TAG, "onSensorChanged" );
Toast.makeText(mContext,"Heelooo" , Toast.LENGTH_SHORT).show();
stopSelf();
}
}
和我的活动为:
public class MainActivity extends Activity {
Intent intent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
intent = new Intent(this, CustomSensorService.class);
}
@Override
public void onResume(){
super.onResume();
startService(intent);
}
}
这是清单
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.learnandroidservice.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name=".CustomSensorService"/>
</application>
跟踪:
Trace:
推荐答案
mContext
为空 - 你需要初始化它,你把它传递给前Toast.makeText()
。
mContext
is null - you need to initialise it before you pass it to Toast.makeText()
.
服务
是一个背景,所以你可以叫
Service
is a context so you can just call
Toast.makeText(this,"Heelooo" , Toast.LENGTH_SHORT).show();
它的工作原理,当你删除你提到因为那时SensorListener从未注册的线条和 onSensorChanged
永远不会被调用。
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