class ActivityCollector {  //var activities :MutableList<Activity>=MutableList<Activity>()  companion object{    val activities = ArrayList<Activity>()    fun addActivity( activity:Activity){      activities.add(activity)    }    fun removeActivity(activity:Activity){      activities.remove(activity)    }    fun finsishAll(){      for(activity:Activity in activities){        if(!activity.isFinishing){          activity.finish()        }      }      activities.clear()    }  }}

open class BaseActivity : AppCompatActivity(){  var activityCollector=ActivityCollector()  lateinit var receiver:ForceOfflineReceiver  override fun onCreate(savedInstanceState: Bundle?, persistentState: PersistableBundle?) {    super.onCreate(savedInstanceState, persistentState)    ActivityCollector.addActivity(this)    //activityCollector.addActivity(this)  }  override fun onResume() {    super.onResume()    var inetnefilter:IntentFilter=IntentFilter()    inetnefilter.addAction("FORCE_FOOLINE")    receiver=ForceOfflineReceiver()    registerReceiver(receiver,inetnefilter)  }  override fun onPause() {    super.onPause()    if(receiver!=null){      unregisterReceiver(receiver)      // receiver=null    }  }  override fun onDestroy() {    super.onDestroy()    ActivityCollector.removeActivity(this)  }  open class ForceOfflineReceiver : BroadcastReceiver(){    override fun onReceive(context: Context, intent: Intent?) {      var builder :AlertDialog.Builder=AlertDialog.Builder(context)      builder.setTitle("Warning")      builder.setMessage("you are forced to be offline .please try to login again")      builder.setCancelable(false)      builder.setPositiveButton("ok",object :DialogInterface.OnClickListener{        override fun onClick(dialog: DialogInterface?, which: Int) {          ActivityCollector.finsishAll()          var intent=Intent(context,LoginActivity::class.java)          context.startActivity(intent)        }      })      builder.show()    }  }}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="vertical"><LinearLayout  android:layout_width="match_parent"  android:layout_height="60dp"  android:orientation="horizontal">  <TextView    android:layout_width="90dp"    android:layout_height="wrap_content"    android:layout_gravity="center_vertical"    android:textSize="18sp"    android:text="account:"    />  <EditText    android:id="@+id/account"    android:layout_width="0dp"    android:layout_height="wrap_content"    android:layout_weight="1"    android:layout_gravity="center_vertical"    /></LinearLayout>  <LinearLayout    android:layout_width="match_parent"    android:layout_height="60dp"    android:orientation="horizontal">    <TextView      android:layout_width="90dp"      android:layout_height="wrap_content"      android:layout_gravity="center_vertical"      android:textSize="18sp"      android:text="password:"      />    <EditText      android:id="@+id/password"      android:layout_width="0dp"      android:layout_height="wrap_content"      android:layout_weight="1"      android:layout_gravity="center_vertical"      android:inputType="textPassword"      />  </LinearLayout>  <Button    android:id="@+id/login"    android:layout_width="match_parent"    android:layout_height="60dp"    android:text="Login"    /></LinearLayout>

class LoginActivity:BaseActivity(){   lateinit var accountEdid:EditText   lateinit var passwordEdit :EditText    lateinit var login:Button  override fun onCreate(savedInstanceState: Bundle?) {    super.onCreate(savedInstanceState)    setContentView(R.layout.login)    accountEdid=findViewById(R.id.account)    passwordEdit=findViewById(R.id.password)    login=findViewById(R.id.login)    login.setOnClickListener(View.OnClickListener {      var account =accountEdid.text.toString()      var password=passwordEdit.text.toString()      if(account.equals("admin")&&password.equals("123")){        var intent:Intent=Intent(this, MainActivity::class.java)        startActivity(intent)        finish()      }else{        Toast.makeText(this,"賬號或密碼錯(cuò)誤",Toast.LENGTH_SHORT).show()      }    })  }}

class MainActivity : BaseActivity() {  override fun onCreate(savedInstanceState: Bundle?) {    super.onCreate(savedInstanceState)    setContentView(R.layout.activity_main)    var forceOffline :Button =findViewById(R.id.force_offline)    forceOffline.setOnClickListener(View.OnClickListener {      var intent:Intent=Intent("FORCE_FOOLINE")      sendBroadcast(intent)    })  }}

<application  android:allowBackup="true"  android:icon="@mipmap/ic_launcher"  android:label="@string/app_name"  android:roundIcon="@mipmap/ic_launcher_round"  android:supportsRtl="true"  android:theme="@style/AppTheme">  <activity android:name=".MainActivity">  </activity>  <activity android:name=".LoginActivity" android:launchMode="singleTask">    <intent-filter>      <action android:name="android.intent.action.MAIN" />      <category android:name="android.intent.category.LAUNCHER" />    </intent-filter>  </activity></application>