받아 들인 답변 ( Duane Homick )에는 처리되지 않은 사례가 있다고 생각합니다 .

다른 추가 기능이 있으며 결과적으로 앱이 중복됩니다.

• 마켓 또는 홈 화면 아이콘 (마켓에서 자동으로 배치됨)에서 애플리케이션을 실행할 때
• 런처 또는 수동으로 만든 홈 화면 아이콘으로 응용 프로그램을 시작할 때

다음은 이러한 사례와 상태 표시 줄 알림도 처리 할 수있는 솔루션 (SDK_INT> = 11 알림)입니다.

매니페스트 :

    <activity
        android:name="com.acme.activity.LauncherActivity"
        android:noHistory="true">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>
    <service android:name="com.acme.service.LauncherIntentService" />

런처 활동 :

public static Integer lastLaunchTag = null;
@Override
public void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    mInflater = LayoutInflater.from(this);
    View mainView = null;
    mainView = mInflater.inflate(R.layout.act_launcher, null); // empty layout
    setContentView(mainView);

    if (getIntent() == null || getIntent().getExtras() == null || !getIntent().getExtras().containsKey(Consts.EXTRA_ACTIVITY_LAUNCH_FIX)) {
        Intent serviceIntent = new Intent(this, LauncherIntentService.class);
        if (getIntent() != null && getIntent().getExtras() != null) {
            serviceIntent.putExtras(getIntent().getExtras());
        }
        lastLaunchTag = (int) (Math.random()*100000);
        serviceIntent.putExtra(Consts.EXTRA_ACTIVITY_LAUNCH_TAG, Integer.valueOf(lastLaunchTag));
        startService(serviceIntent);

        finish();
        return;
    }

    Intent intent = new Intent(this, SigninActivity.class);
    if (getIntent() != null && getIntent().getExtras() != null) {
        intent.putExtras(getIntent().getExtras());
    }
    startActivity(intent);
}

서비스 :

@Override
protected void onHandleIntent(final Intent intent) {
    Bundle extras = intent.getExtras();
    Integer lastLaunchTag = extras.getInt(Consts.EXTRA_ACTIVITY_LAUNCH_TAG);

    try {
        Long timeStart = new Date().getTime();
        while (new Date().getTime() - timeStart < 100) {
            Thread.currentThread().sleep(25);
            if (!lastLaunchTag.equals(LauncherActivity.lastLaunchTag)) {
                break;
            }
        }
        Thread.currentThread().sleep(25);
        launch(intent);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

private void launch(Intent intent) {
    Intent launchIintent = new Intent(LauncherIntentService.this, LauncherActivity.class);
    launchIintent.addCategory(Intent.CATEGORY_LAUNCHER);
    launchIintent.setAction(Intent.ACTION_MAIN);
    launchIintent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    launchIintent.addFlags(Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);
    if (intent != null && intent.getExtras() != null) {
        launchIintent.putExtras(intent.getExtras());
    }
    launchIintent.putExtra(Consts.EXTRA_ACTIVITY_LAUNCH_FIX, true);
    startActivity(launchIintent);
}

알림 :

ComponentName actCN = new ComponentName(context.getPackageName(), LauncherActivity.class.getName());
Intent contentIntent = new Intent(context, LauncherActivity.class);
contentIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
if (Build.VERSION.SDK_INT >= 11) {
    contentIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK); // if you need to recreate activity stack
}
contentIntent.addCategory(Intent.CATEGORY_LAUNCHER);
contentIntent.setAction(Intent.ACTION_MAIN);
contentIntent.putExtra(Consts.EXTRA_CUSTOM_DATA, true);

답변

protected override void OnCreate(Bundle bundle) {
    base.OnCreate(bundle);

    Xamarin.Forms.Forms.Init(this, bundle);
    LoadApplication(new App());

    if(!IsTaskRoot) {
        Intent intent = Intent;
        string action = intent.Action;
        if(intent.HasCategory(Intent.CategoryLauncher) && action != null && action.Equals(Intent.ActionMain, System.StringComparison.OrdinalIgnoreCase)) {
            System.Console.WriteLine("\nIn APP.Droid.MainActivity.OnCreate() - Finishing Activity and returning since a second MainActivity has been created.\n");
            Finish();
            return; //Not necessary if there is no code below
        }
    }
}

ActivityManager manager = (ActivityManager) this.getSystemService( ACTIVITY_SERVICE );
List<RunningTaskInfo> tasks =  manager.getRunningTasks(Integer.MAX_VALUE);

for (RunningTaskInfo taskInfo : tasks) {
    if(taskInfo.baseActivity.getClassName().equals(<your package name>.<your class name>) && (taskInfo.numActivities > 1)){
        finish();
    }
}

< uses-permission android:name="android.permission.GET_TASKS" />