Life cycle of activity

The life cycle of Android learning activity

Android apps cannot control their own processes themselves, but the Android runtime can manage each process. Therefore, the correct understanding of the life of activity, to ensure that users have a good experience has a great help.

1. Activity stack and statusThe activity stack is a collection of all activity LIFO that is currently running. The newly started activity is always at the top of the stack. Activity has four states.

• Active State When the activity is at the top of the stack, that is, activity is visible, with focus on the activity, you can accept user input at this time. Under normal circumstances, the Android runtime will try to keep the activity from being terminated.
• paused state the activity at this time is visible, but it has no focus. When a transparent or non-full-screen activity is in the current activity, activity is paused. Activity in this state is approximately active state. If memory is not required, normally it will not be terminated by runtime.
• Stop state When an activity is in a stopped state, it is not visible. But it is still in memory, saving the state of the current activity. When memory is needed elsewhere, the activity of this state is the preferred terminating object.

Inactive State After the activity is terminated, it is inactive. Activity in this state has been removed from the activity stack. To show activity in this state, you need to restart the activity.

life cycle of 2.Activitythe life cycle diagram of the activity is shown below.

3.MainActivity

1  PackageCom.example.zhouy.android4exercise;2 3 Importandroid.app.Activity;4 ImportAndroid.content.DialogInterface;5 ImportAndroid.content.Intent;6 ImportAndroid.os.Bundle;7 ImportAndroid.os.PersistableBundle;8 ImportAndroid.support.v7.app.AlertDialog;9 ImportAndroid.util.Log;Ten ImportAndroid.view.View; One ImportAndroid.widget.Button; A  -  Public classMainactivityextendsActivityImplementsview.onclicklistener{ -  the     PrivateButton malertbtn =NULL; -  -     PrivateButton mjumpbtn =NULL; -  +@Override -     protected voidOnCreate (Bundle savedinstancestate) { +         Super. OnCreate (Savedinstancestate); ASetcontentview (R.layout.activity_main); atMALERTBTN = (Button) Findviewbyid (R.id.alert_dialog); -Malertbtn.setonclicklistener ( This); -MJUMPBTN = (Button) Findviewbyid (r.id.jump_to_another_activity); -Mjumpbtn.setonclicklistener ( This); -LOG.V ("Tag","onCreate ()"); -} in  -     Private voidAlertdialog () { to         the activity's life cycle does not change when the activity is used to pop up a dialog box.  +         FinalAlertdialog.builder Builder =NewAlertdialog.builder ( This); -Builder.settitle ("dialog box title"); theBuilder.setmessage ("dialog box Contents"); *Builder.setpositivebutton ("OK",NewDialoginterface.onclicklistener () { $@OverridePanax Notoginseng              Public voidOnClick (Dialoginterface Dialoginterface,inti) { -LOG.V ("Tag","Ok"); the} +}); ABuilder.setnegativebutton ("cancle",NewDialoginterface.onclicklistener () { the@Override +              Public voidOnClick (Dialoginterface Dialoginterface,inti) { -LOG.V ("Tag","Cancel"); $} $}); -Builder.create (); -Builder.show (); the  -}Wuyi  the     Private voidGotonextactivity () { -Intent Intent =NewIntent ( This, Nextactivity.class); WuStartActivity (Intent); -} About@Override $     protected voidOnrestart () { -         Super. Onrestart (); -LOG.V ("Tag","Onrestart ()"); -} A  +@Override the     protected voidOnrestoreinstancestate (Bundle savedinstancestate) { -         Super. Onrestoreinstancestate (Savedinstancestate); $LOG.V ("Tag","onrestoreinstancestate"); the} the  the@Override the     protected voidOnStart () { -         Super. OnStart (); inLOG.V ("Tag","OnStart ()"); the  the} About  the@Override the     protected voidOnresume () { the         Super. Onresume (); +LOG.V ("Tag","Onresume ()"); -  the}Bayi  the  the@Override -     protected voidOnPause () { -         Super. OnPause (); theLOG.V ("Tag","OnPause ()"); the  the} the  -@Override the      Public voidOnsaveinstancestate (Bundle outstate, Persistablebundle outpersistentstate) { the         Super. Onsaveinstancestate (Outstate, outpersistentstate); theLOG.V ("Tag","onsaveinstancestate");94} the  the@Override the     protected voidOnStop () {98         Super. OnStop (); AboutLOG.V ("Tag","onStop ()"); - 101}102 103@Override104     protected voidOnDestroy () { the         Super. OnDestroy ();106LOG.V ("Tag","ondestory ()");107 108}109  the@Override111      Public voidOnClick (view view) { the         intid = View.getid ();113         if(id = = R.id.alert_dialog) { theAlertdialog (); the}Else if(id = = r.id.jump_to_another_activity) { theGotonextactivity ();117}118}119} - 

4.activity_main.xml

1 <?XML version= "1.0" encoding= "Utf-8"?>2 <Relativelayout xmlns:Android="Http://schemas.android.com/apk/res/android"3     xmlns:Tools="Http://schemas.android.com/tools"4     Android:Layout_width="Match_parent"5     Android:Layout_height="Match_parent"6     Android:Paddingbottom="@dimen/activity_vertical_margin"7     Android:paddingleft="@dimen/activity_horizontal_margin"8     Android:paddingright="@dimen/activity_horizontal_margin"9     Android:paddingtop="@dimen/activity_vertical_margin"

Ten     Tools:Context="Com.example.zhouy.android4exercise.MainActivity"> One     <Button A         Android:ID="@+id/alert_dialog" -         Android:Layout_alignparenttop="true" -         Android:Layout_width="Match_parent" the         Android:Layout_height="Wrap_content" -         Android:text="Pop-up dialog box"/> -     <Button -         Android:ID="@+id/jump_to_another_activity" +         Android:Layout_below="@id/alert_dialog" -         Android:Layout_width="Match_parent" +         Android:Layout_height="Wrap_content" A         Android:text="Jump to another activity"/> at  - </Relativelayout>

Life cycle of activity