先利用以前所学的知识，创建一个活动的管理类ActivityCollector：
public class ActivityCollector{ public static List<Activity> activities = new ArrayList<Activity>(); public static void addActivity(Activity activity){ activities.add(activity); } public static void removeActivity(Activity activity){ activities.remove(activity); } public static void finishAll(){ for(Activity activity : activities){ if(activity.isFinishing()){ actiivty.finish(); } } } }接下来创建所有活动的父类BaseActivity：
public class BaseActivity extends Activity{ @Override protected void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); ActivityCollector.addActivity(this); } @Override protected void onDestroy(){ super.onDestroy(); ActivityCollector.removeActivity(this); } }接来下创建一个登陆的界面：
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:stretchColumns="1" > <TableRow > <TextView android:layout_height="wrap_content" android:text="Account:"/> <EditText android:id="@+id/aaccount" android:layout_height="wrap_content" android:hint="Input yout acction"/> </TableRow> <TableRow > <TextView android:layout_height="wrap_content" android:text="Password:"/> <EditText android:id="@+id/password" android:layout_height="wrap_content" android:inputType="textPassword" android:hint="Input your password"/> </TableRow> <TableRow > <Button android:id="@+id/login" android:layout_height="wrap_content" android:layout_span="2" android:text="Login"/> </TableRow> </TableLayout>创建LoginActivity，并继承BaseActivity：
public class LoginActivity extends BaseActivity{ private EditText accountEdit; private EditText passwordEdit; private Button button; @Override protected void onCreate(Bundle savedInstanceState){ accountEdit = (EditText)findViewById(R.id.account); passwordEdit = (EditText)findViewById(R.id.password); button = (Button)findViewById(R.id.login); button.setOnClickListener(new OnClickListener(){ String account = accountEdit.getText().toString(); String password = passwordEdit.getText().toString(); if("admin".equals(account) && "1111".equals(password)){ Intent intent = new Intent(LoginActivity.this, MainActivity.class); startActivity(intent); }else{ Toast.make(LoginActivity.this, "account or password is invalid", Toast.LENGTH_SHORT).show(); } }); } }在activity_main.xml文件中添加一个button，用于点击button之后弹出强制退出活动的dialog的功能，button的布局代码在这不做编写，关键是MainActivity中发送广播的代码配置：
public class MainActivity extends BaseActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Button button = (Button)findViewById(R.id.button); button.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Intent intent = new Intent("com.zhaojy.androidstu_broadcastbestpractice.FORCE_OFFLINE"); sendBroadcast(intent); } }); } }MainActivity中发送了强制下线的广播以后就要在广播接收器中响应动作，新建forceOfflineReceiver的广播接收器：
public class ForceOfflineReceiver extends BroadcastReceiver{ @Override public void onReceive(final Context context, Intent intent) { AlertDiglog.Builder dialogBuilder = new AlertDiglog.Builder(context); dialogBuilder.setTitle("Warning"); dialogBuilder.setMessage("You are forced to be offline. Please try to login again"); dialogBuilder.setCancelable(false); dialogBuilder.setPositiveButton("OK", new OnClickListener(){ @Override public void onClick(DialogInterface dialog, int which){ ActivityCollector.finishAll(); Intent intent = new Intent(context, LoginActivity.calss); intent.addFalgs(Intent.FLAG_ACTIVITY_NEW_TASK); context.startActivity(intent); /** * 由于我们是在广播接收器里启动活动的，因此一定要给 * Intent 加入 FLAG_ACTIVITY_NEW_TASK 这个标志。最后，还需要把对话框的类型设为 * TYPE_SYSTEM_ALERT，不然它将无法在广播接收器里弹出 */ } }); AlertDialog alertDialog = dialogBuilder.create(); alertDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT); alertDialog,show(); } }注意： 1.由于我们是在广播接收器里启动活动的，因此一定要给 Intent加入FLAG_ACTIVITY_NEW_TASK这个标志。最后，还需要把对话框的类型设为； TYPE_SYSTEM_ALERT，不然它将无法在广播接收器里弹出. 2.由于我们在 ForceOfflineReceiver 里弹出了一个系统级别 的对话框，因此必须要声明android.permission.SYSTEM_ALERT_WINDOW 权限； 3.将LoginActivity设为主活动； 4.对ForceOfflineReceiver进行注册，指定接收com.zhaojy.androidstu_broadcastbestpractice.FORCE_OFFLINE这个广播。
