片段的lifeCycle混淆

Question

我有一个mainActivity，它承载一个ViewPager并包含三个Tabs (MQTT、ECO、Logger)。mainActivity有生命周期回调(onCreat、onResume)，其他三个选项卡有片段‘lifeCycle回调(onattached、onCreateView、onViewcreated、onResume、onPause)。

在运行时，我在logCat中接收以下内容：

01-29 13:28:28.732: W/MainActivity(31412): @onCreate().
01-29 13:28:28.802: W/MainActivity(31412): @onResume().
01-29 13:28:28.842: W/MQTT_Settings_Frag(31412): @onAttach().
01-29 13:28:28.842: W/MQTT_Settings_Frag(31412): @onCreateView().
01-29 13:28:28.862: W/MQTT_Settings_Frag(31412): @onViewCreated().
01-29 13:28:28.862: W/MQTT_Settings_Frag(31412): @onResume().
01-29 13:28:28.862: W/Eco_Settings_Frag(31412): @onAttach().
01-29 13:28:28.862: W/Eco_Settings_Frag(31412): @onCreateView().
01-29 13:28:28.892: W/Eco_Settings_Frag(31412): @onViewCreated().
01-29 13:28:28.892: W/Eco_Settings_Frag(31412): @onResume().

当我滑动到Eco选项卡“第二个”时，logCa没有报告任何片段，但是当我滑动到第三个选项卡"Logger"-which已经实现- logCat显示：

01-29 13:37:27.062: W/MQTT_Settings_Frag(31412): @onPause().

当我从Logger-选项卡滑回Eco-Tab时，LogCat将执行以下操作：

01-29 13:37:52.292: W/MQTT_Settings_Frag(31412): @onCreateView().
01-29 13:37:52.322: W/MQTT_Settings_Frag(31412): @onViewCreated().
01-29 13:37:52.322: W/MQTT_Settings_Frag(31412): @onResume().


why the first tab "MQTT-Tab" goes in onPause() when i goto only to the third Tab Logger-Tab?
And why the first tab "MQTT-Tab" goes into (onCreateView, onViewCreated, onResume) when i move to the secondtab Eco-tab frm the third one LoggerTab?

Answer 1

默认情况下，ViewPager只在内存中保留相邻的选项卡，因此，当您转到第三个选项卡时，第一个选项卡就会被销毁，当您回到中间时重新创建该选项卡。您可以通过使用yourViewPager.setOffscreenPageLimit(int)来改变这种行为。