SensorEventListener實現不起作用

我想在我的簡單活動中使用SensorEventListener，但每次運行應用程序後都會失敗。SensorEventListener實現不起作用

下面是活動代碼：

package com.chovanec.elastix; 

import android.hardware.Sensor; 
import android.hardware.SensorEvent; 
import android.hardware.SensorEventListener; 
import android.hardware.SensorManager; 
import android.os.Bundle; 
import android.app.Activity; 
import android.util.Log; 
import android.view.Menu; 

public class MainActivity extends Activity implements SensorEventListener { 

    private final SensorManager m_sensor_manager; 
    private final Sensor m_accelerometer; 

    public MainActivity() 
    { 
     m_sensor_manager = (SensorManager) getSystemService(SENSOR_SERVICE); 
     m_accelerometer = m_sensor_manager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); 
    } 

    @Override 
    protected void onCreate(Bundle savedInstanceState) 
    { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) 
    { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.activity_main, menu); 
     return true; 
    } 

    protected void onResume() 
    { 
     super.onResume(); 
     m_sensor_manager.registerListener(this, m_accelerometer, SensorManager.SENSOR_DELAY_NORMAL); 
    } 

    public void onSensorChanged(SensorEvent event) 
    { 
     _("onSensorChanged"); 
     _("" + event.values[0]); 
    } 

    public void onAccuracyChanged(Sensor sensor, int accuracy) 
    { 

    } 

    private void _(String msg) 
    { 
     Log.d("chovanec", msg); 
    } 

}

這裏是目錄下載：

04-01 19:25:16.755: D/AndroidRuntime(19142): Shutting down VM 
04-01 19:25:16.755: W/dalvikvm(19142): threadid=1: thread exiting with uncaught exception (group=0x40f3e2a0) 
04-01 19:25:16.765: E/AndroidRuntime(19142): FATAL EXCEPTION: main 
04-01 19:25:16.765: E/AndroidRuntime(19142): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.chovanec.elastix/com.chovanec.elastix.MainActivity}: java.lang.IllegalStateException: System services not available to Activities before onCreate() 
04-01 19:25:16.765: E/AndroidRuntime(19142): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2024) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at android.app.ActivityThread.access$600(ActivityThread.java:140) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at android.os.Handler.dispatchMessage(Handler.java:99) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at android.os.Looper.loop(Looper.java:137) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at android.app.ActivityThread.main(ActivityThread.java:4898) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at java.lang.reflect.Method.invokeNative(Native Method) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at java.lang.reflect.Method.invoke(Method.java:511) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at dalvik.system.NativeStart.main(Native Method) 
04-01 19:25:16.765: E/AndroidRuntime(19142): Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate() 
04-01 19:25:16.765: E/AndroidRuntime(19142): at android.app.Activity.getSystemService(Activity.java:4603) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at com.chovanec.elastix.MainActivity.<init>(MainActivity.java:19) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at java.lang.Class.newInstanceImpl(Native Method) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at java.lang.Class.newInstance(Class.java:1319) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at android.app.Instrumentation.newActivity(Instrumentation.java:1057) 
04-01 19:25:16.765: E/AndroidRuntime(19142): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2015) 
04-01 19:25:16.765: E/AndroidRuntime(19142): ... 11 more

來源

2013-04-01 Michal

上面清清楚楚地寫着

 
Caused by: java.lang.IllegalStateException: 
System services not available to Activities before onCreate()

有沒有在活動構造函數的概念。將您的代碼轉移到您的活動的onCreate方法。

 
m_sensor_manager = (SensorManager) getSystemService(SENSOR_SERVICE); 
m_accelerometer = m_sensor_manager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

來源

2013-04-01 17:36:10

什麼代碼必須移動到onCreate？ – Michal

刪除以下代碼：

public MainActivity() 
{ 
    m_sensor_manager = (SensorManager) getSystemService(SENSOR_SERVICE); 
    m_accelerometer = m_sensor_manager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); 
}

，並把的onCreate內的那些行（）。

@Override 
protected void onCreate(Bundle savedInstanceState) 
{ 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    m_sensor_manager = (SensorManager) getSystemService(SENSOR_SERVICE); 
    m_accelerometer = m_sensor_manager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); 
}

來源

2013-04-01 17:44:46

這是不正確的： m_sensor_manager =（的SensorManager）getSystemService（SENSOR_SERVICE）;

像這樣使用： m_sensor_manager =（SensorManager）getSystemService（Context.SENSOR_SERVICE）;

來源

2015-02-14 07:25:03

SensorEventListener實現不起作用

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