Java 从后台以编程方式恢复Android活动的问题

我试图从后台以编程方式恢复Android活动，但当我按下home按钮时，活动在五秒钟后进入后台，活动再次启动。与后退按钮和最近的应用程序按钮配合良好

为什么它会延迟5秒重新启动

API级别为19，Android版本为4.4.2（KitKat）

以下是代码：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.test.drawtoptest">

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

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Main2Activity"
            android:label="@string/app_name"
            android:parentActivityName=".Main2Activity"
            >
        </activity>

    </application>

</manifest>

public class MainActivity extends AppCompatActivity {

  MyTimerTask myTimerTask;
    Timer timer;
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = (Button) findViewById(R.id.button);
        Button button1 = (Button) findViewById(R.id.button3);
    }
  public void test(){
      Intent myIntent = new Intent(getBaseContext(), MainActivity.class);
        myIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP|Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_SINGLE_TOP|Intent.FLAG_ACTIVITY_SINGLE_TOP);
        startActivity(myIntent);
    }
 class MyTimerTask extends TimerTask {
        @Override
        public void run() {

            test();
        }
    }


    @Override
    protected void onPause(){
        if (timer == null) {
            myTimerTask = new MyTimerTask();
            timer = new Timer();
            timer.schedule(myTimerTask, 50, 50);
        }
        super.onPause();

    }
}