关于onSaveInstanceState(Bundle)和onRestoreInstanceState(Bundle)

最新推荐文章于 2025-08-14 23:47:29 发布

最新推荐文章于 2025-08-14 23:47:29 发布 · 73 阅读

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本文深入解析Android Activity生命周期中两个关键方法：onSaveInstanceState和onRestoreInstanceState的作用、实现原理及使用场景。帮助开发者更好地理解和运用这两个方法，确保应用程序在不同状态变化时的数据完整性和用户体验连续性。

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关于activity的方法onSaveInstanceState(Bundle)和onRestoreInstanceState(Bundle)).
protectedvoidonSaveInstanceState(<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/os/Bundle.html" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">Bundle</a>outState) Calledtoretrieveper-instancestatefromanactivitybeforebeingkilledsothatthestatecanberestoredin<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onCreate%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onCreate(Bundle)</a>or<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onRestoreInstanceState%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onRestoreInstanceState(Bundle)</a>(the<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/os/Bundle.html" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">Bundle</a>populatedbythismethodwillbepassedtoboth). Thismethodiscalledbeforeanactivitymaybekilledsothatwhenitcomesbacksometimeinthefutureitcanrestoreitsstate.Forexample,ifactivityBislaunchedinfrontofactivityA,andatsomepointactivityAiskilledtoreclaimresources,activityAwillhaveachancetosavethecurrentstateofitsuserinterfaceviathismethodsothatwhentheuserreturnstoactivityA,thestateoftheuserinterfacecanberestoredvia<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onCreate%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onCreate(Bundle)</a>or<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onRestoreInstanceState%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onRestoreInstanceState(Bundle)</a>. Donotconfusethismethodwithactivitylifecyclecallbackssuchas<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onPause%28%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onPause()</a>,whichisalwayscalledwhenanactivityisbeingplacedinthebackgroundoronitswaytodestruction,or<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onStop%28%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onStop()</a>whichiscalledbeforedestruction.Oneexampleofwhen<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onPause%28%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onPause()</a>and<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onStop%28%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onStop()</a>iscalledandnotthismethodiswhenausernavigatesbackfromactivityBtoactivityA:thereisnoneedtocall<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onSaveInstanceState%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onSaveInstanceState(Bundle)</a>onBbecausethatparticularinstancewillneverberestored,sothesystemavoidscallingit.Anexamplewhen<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onPause%28%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onPause()</a>iscalledandnot<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onSaveInstanceState%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onSaveInstanceState(Bundle)</a>iswhenactivityBislaunchedinfrontofactivityA:thesystemmayavoidcalling<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onSaveInstanceState%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onSaveInstanceState(Bundle)</a>onactivityAifitisn'tkilledduringthelifetimeofBsincethestateoftheuserinterfaceofAwillstayintact. ThedefaultimplementationtakescareofmostoftheUIper-instancestateforyoubycalling<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/view/View.html#onSaveInstanceState%28%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onSaveInstanceState()</a>oneachviewinthehierarchythathasanid,andbysavingtheidofthecurrentlyfocusedview(allofwhichisrestoredbythedefaultimplementationof<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onRestoreInstanceState%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onRestoreInstanceState(Bundle)</a>).Ifyouoverridethismethodtosaveadditionalinformationnotcapturedbyeachindividualview,youwilllikelywanttocallthroughtothedefaultimplementation,otherwisebepreparedtosaveallofthestateofeachviewyourself. Ifcalled,thismethodwilloccurbefore<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onStop%28%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onStop()</a>.Therearenoguaranteesaboutwhetheritwilloccurbeforeorafter<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onPause%28%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onPause()</a>. 如果onSaveInstanceState要被调用的话，只能保证它在stop之前调用。但它可以在onPause（）之前OR之后调用。 注：应该说active要被杀死才调用该函数。但是按back键不会调用。通过finish()结束active也不会调用onSaveInstanceState。因为既然销毁后无法重生，就没必要调用onSaveInstanceState来保存protected <div style="line-height:25px"> voidonRestoreInstanceState(<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/os/Bundle.html" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">Bundle</a>savedInstanceState) </div> <div style="line-height:25px">Thismethodiscalledafter<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onStart%28%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none; font-weight:bold">onStart()</a>whentheactivityisbeingre-initializedfromapreviouslysavedstate,givenhereinsavedInstanceState.Mostimplementationswillsimplyuse<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onCreate%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onCreate(Bundle)</a>torestoretheirstate,butitissometimesconvenienttodoithereafteralloftheinitializationhasbeendoneortoallowsubclassestodecidewhethertouseyourdefaultimplementation.Thedefaultimplementationofthismethodperformsarestoreofanyviewstatethathadpreviouslybeenfrozenby<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onSaveInstanceState%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onSaveInstanceState(Bundle)</a>.Thismethodiscalledbetween<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onStart%28%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onStart()</a>and<a target="_blank" rel="nofollow" href="http://developer.android.com/reference/android/app/Activity.html#onPostCreate%28android.os.Bundle%29" style="color:rgb(207,121,28); line-height:25px; text-decoration:none">onPostCreate(Bundle)</a>. 注1:savedInstanceState就是在onSaveInstanceState中报存下来的Bundle. 注2：其实也可以在oncreate中读取在onSaveInstanceState中报存下来的Bundle。但是在onRestoreInstanceState中处理也有些方便的地方。至少要好看些吧。 </div>