java - ble beacon transmitter app close once it run -


i trying create app transmit beacons android 5.0 devices error 

{09-07 10:23:45.184 3057-3057/com.example.mohamed_pc.test2 e/androidruntime: fatal exception: main                                                                             process: com.example.mohamed_pc.test2, pid: 3057                                                                             java.lang.runtimeexception: unable start activity componentinfo{com.example.mohamed_pc.test2/com.example.mohamed_pc.test2.mainactivity}: java.lang.nullpointerexception: attempt invoke virtual method 'android.bluetooth.le.bluetoothleadvertiser android.bluetooth.bluetoothadapter.getbluetoothleadvertiser()' on null object reference                                                                                 @ android.app.activitythread.performlaunchactivity(activitythread.java:2416)                                                                                 @ android.app.activitythread.handlelaunchactivity(activitythread.java:2476)                                                                                 @ android.app.activitythread.-wrap11(activitythread.java)                                                                                 @ android.app.activitythread$h.handlemessage(activitythread.java:1344)                                                                                 @ android.os.handler.dispatchmessage(handler.java:102)                                                                                 @ android.os.looper.loop(looper.java:148)                                                                                 @ android.app.activitythread.main(activitythread.java:5417)                                                                                 @ java.lang.reflect.method.invoke(native method)                                                                                 @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:726)                                                                                 @ com.android.internal.os.zygoteinit.main(zygoteinit.java:616)                                                                              caused by: java.lang.nullpointerexception: attempt invoke virtual method 'android.bluetooth.le.bluetoothleadvertiser android.bluetooth.bluetoothadapter.getbluetoothleadvertiser()' on null object reference                                                                                 @ com.example.mohamed_pc.test2.mainactivity.oncreate(mainactivity.java:31)                                                                                 @ android.app.activity.performcreate(activity.java:6237)                                                                                 @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1107)                                                                                 @ android.app.activitythread.performlaunchactivity(activitythread.java:2369)                                                                                 @ android.app.activitythread.handlelaunchactivity(activitythread.java:2476)                                                                                  @ android.app.activitythread.-wrap11(activitythread.java)                                                                                  @ android.app.activitythread$h.handlemessage(activitythread.java:1344)                                                                                  @ android.os.handler.dispatchmessage(handler.java:102)                                                                                  @ android.os.looper.loop(looper.java:148)                                                                                  @ android.app.activitythread.main(activitythread.java:5417)                                                                                  @ java.lang.reflect.method.invoke(native method)                                                                                  @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:726)                                                                                  @ com.android.internal.os.zygoteinit.main(zygoteinit.java:616) }

the code below

package com.example.mohamed_pc.test2;   import android.bluetooth.bluetoothadapter; import android.bluetooth.le.advertisecallback; import android.bluetooth.le.advertisedata; import android.bluetooth.le.advertisesettings; import android.bluetooth.le.bluetoothleadvertiser; import android.os.bundle; import android.support.v7.app.appcompatactivity; import android.view.view; import android.widget.button; import java.nio.bytebuffer; import java.util.uuid;    public class mainactivity extends appcompatactivity {    private bluetoothadapter mbluetoothadapter;     private bluetoothleadvertiser mbluetoothleadvertiser;    private advertisedata madvertisedata;     private advertisesettings madvertisesettings;     private advertisecallback madvertisecallback;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         mbluetoothadapter = bluetoothadapter.getdefaultadapter();        mbluetoothleadvertiser = mbluetoothadapter.getbluetoothleadvertiser();     }      public void buttononclick(view v) { // when button clicked         button button=(button) v;         ((button) v).settext("clicked");         setadvertisedata();         setadvertisesettings();         mbluetoothleadvertiser.startadvertising(madvertisesettings, madvertisedata, madvertisecallback);      }     protected void setadvertisedata() {         advertisedata.builder mbuilder = new advertisedata.builder();         bytebuffer mmanufacturerdata = bytebuffer.allocate(24);         byte[] uuid = getidasbyte(uuid.fromstring("0cf052c297ca407c84f8b62aac4e9020"));         mmanufacturerdata.put(0, (byte)0xbe); // beacon identifier         mmanufacturerdata.put(1, (byte)0xac); // beacon identifier         (int i=2; i<=17; i++) {             mmanufacturerdata.put(i, uuid[i-2]); // adding uuid         }         mmanufacturerdata.put(18, (byte)0x00); // first byte of major         mmanufacturerdata.put(19, (byte)0x09); // second byte of major         mmanufacturerdata.put(20, (byte)0x00); // first minor         mmanufacturerdata.put(21, (byte)0x06); // second minor         mmanufacturerdata.put(22, (byte)0xb5); // txpower         mbuilder.addmanufacturerdata(224, mmanufacturerdata.array()); // using google's company id         madvertisedata = mbuilder.build();     }     protected void setadvertisesettings() {         advertisesettings.builder mbuilder = new advertisesettings.builder();         mbuilder.setadvertisemode(advertisesettings.advertise_mode_low_power);         mbuilder.setconnectable(false);         mbuilder.settimeout(0);         mbuilder.settxpowerlevel(advertisesettings.advertise_tx_power_medium);         madvertisesettings = mbuilder.build();     }     public static byte[] getidasbyte(java.util.uuid uuid)     {         bytebuffer bb = bytebuffer.wrap(new byte[16]);         bb.putlong(uuid.getmostsignificantbits());         bb.putlong(uuid.getleastsignificantbits());         return bb.array();     }  } 

mbluetoothadapter = bluetoothadapter.getdefaultadapter();

is giving null. check permisses , if bluetooth enabled


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