Question

我第一次在Android上使用服务，我阅读了所有文档和示例，我想从活动中实现绑定服务，我的服务扫描可用的wifi网络和我的活动获取wifi列表，但我卡住了，我不＆＃ 39;知道我的错误在哪里，我的日志说无法启动活动nullpointerexception。清单是可以的，活动和服务是在不同的包。这是我的代码：Activity，然后是Service

 public class StarterService extends Activity {

    final String tag = "WifiConn:...";
    //EditText txt;
    WifiManager myWifi;
    ScanService scan;
    List<ScanResult> sRedes;
    //private ScanService scan;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        doBindService();
            scan=new ScanService();
        //sRet.clear();
        sRedes=scan.getWifi();

        for (int i=0; i<sRedes.size(); i++)
        {
            ScanResult retS = sRedes.get(i); 
           // txt.append("resT: " + retS.SSID +" " + retS.BSSID + "\n");
            Log.d(tag, "resT: " + retS.SSID +" " + retS.BSSID);

            if (retS.SSID.equalsIgnoreCase("Red1"))
            {
              //  txt.append("Red encontrada: " + retS.SSID +" " + retS.BSSID + "\n");
                WifiConfiguration wc = new WifiConfiguration();

                wc.allowedKeyManagement.set(WifiConfiguration.KeyMgmt.NONE);
                wc.SSID = "\""+retS.SSID+"\"";
                wc.BSSID = retS.BSSID;
                wc.status = WifiConfiguration.Status.ENABLED;
                wc.hiddenSSID = true;

                int netID = myWifi.addNetwork(wc); // añade red
              //  txt.append("NetID"+ Integer.toString(netID) +"\n");

                if(myWifi.enableNetwork(netID, true)) // Valida conexión
                {
               //     txt.append("Estado conexión: Ok\n");

                    Log.d("Servicio", "Activado");
                } 
            } else {
            //  txt.append("No encontrado: Ok\n");
                Log.d("Servicio", "Activado");
                //this.stopSelf();
            }
        }
    }


    private ServiceConnection mConnection=new ServiceConnection(){
        public void onServiceConnected(ComponentName classname, IBinder binder){
            scan=((ScanService.MyBinder)binder).getService();
    Toast.makeText(StarterService.this, "Corriendo",     Toast.LENGTH_SHORT).show();
        }

        public void onServiceDisconnected(ComponentName classname) {
            scan= null;

        }
    };

    protected void doBindService() {

bindService(new Intent(this, ScanService.class), mConnection, Context.BIND_AUTO_CREATE);

    } }

此处服务

public class ScanService extends Service {

Timer timer = new Timer();
EditText txt;
WifiManager mWifi;
private static final long UPDATE_INTERVAL = 5000;
private final IBinder mBinder = new MyBinder();
final String tag = "WifiConn:...";
private List<ScanResult> sRet;


public void onCreate() {
    super.onCreate();
    timerScan();
}

private void timerScan(){

    timer.scheduleAtFixedRate(new TimerTask(){
        public void run(){
            mWifi = (WifiManager)getSystemService(Context.WIFI_SERVICE);
            mWifi.startScan();  //Inicio Scan

            Log.d("Service", "Inicio Scan()");
            sRet = mWifi.getScanResults();  //ResultadosScan

        } 
},0,UPDATE_INTERVAL);
    Toast.makeText(this, "Servicio Iniciado", Toast.LENGTH_LONG).show();
    Log.i(getClass().getSimpleName(),"Tiempo iniciado");
}

@Override
public IBinder onBind(Intent arg0) {
return mBinder;
}

public class MyBinder extends Binder {
    public ScanService getService(){
        return ScanService.this;
    }
}
@Override
public void onDestroy() {
    // TODO Auto-generated method stub
    super.onDestroy();
    Log.d("Servicio", "Destruido");
    }

public List<ScanResult> getWifi(){

    return sRet;
} }

当我调试时，错误出现在Activity：

上

doBindService();
sRedes=scan.getWifi();

我的日志

03-24 00:24:46.814: E/AndroidRuntime(20798): FATAL EXCEPTION: main
03-24 00:24:46.814: E/AndroidRuntime(20798): Process: red1.pe, PID: 20798
03-24 00:24:46.814: E/AndroidRuntime(20798): java.lang.RuntimeException: Unable to start activity ComponentInfo{wigo.pe/wigo.pe.StarterService}: java.lang.NullPointerException
03-24 00:24:46.814: E/AndroidRuntime(20798):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2269)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at android.app.ActivityThread.access$800(ActivityThread.java:139)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at android.os.Handler.dispatchMessage(Handler.java:102)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at android.os.Looper.loop(Looper.java:136)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at android.app.ActivityThread.main(ActivityThread.java:5102)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at java.lang.reflect.Method.invokeNative(Native Method)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at java.lang.reflect.Method.invoke(Method.java:515)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at dalvik.system.NativeStart.main(Native Method)
03-24 00:24:46.814: E/AndroidRuntime(20798): Caused by: java.lang.NullPointerException
03-24 00:24:46.814: E/AndroidRuntime(20798):    at wigo.pe.StarterService.onCreate(StarterService.java:35)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at android.app.Activity.performCreate(Activity.java:5248)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1110)
03-24 00:24:46.814: E/AndroidRuntime(20798):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2173)
03-24 00:24:46.814: E/AndroidRuntime(20798):    ... 11 more

Answer 1

您的Service实例没问题。没有问题。

问题是您没有初始化EditText实例txt。在使用onCreate()执行任何操作之前，在txt方法中对其进行初始化。

另一件事，在初始化任何View之前，使用`setContentView（）'方法将布局设置为Activity。

EditText txt;

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

    txt = (EditText) findViewById(R.id.edittext);

   ...........
}

Answer 2

在 ScanService 类中为ScanService构建构造函数。

public ScanService() {

}

现在在您的活动中进行initiazlize

scan = new ScanService();
sRedes=scan.getWifi();

使用onBind方法并且无法启动活动nullpointerexception Android

2 个答案: