Life cycle of Android--activity (i.)

<span id="Label3"></p>1. Activity creation Process 1, 1 Create an activity <ul> <ul> <li>Create a class to inherit from activity</li> <li>Override the OnCreate () method to set the layout</li> <li>Register the activity in the Androimanifest.xml file</li> </ul> </ul>1, 2 Activity7 An important method <ul> <ul> <li>Oncreate– called when first created</li> <li>onstart– at startup</li> <li>When the onresume– gets focus</li> <li>onpause– transfer to other activity or hibernation, etc.</li> <li>onstop– Current activity is not visible</li> <li>onrestart– when restarting</li> <li>ondestory– when destroyed</li> </ul> </ul>2. Single Activity life cycle<p><p>To confirm the conclusion correctly, we create a new activity named fisrt, and rewrite the above 7 methods. and prints the method that is currently called in each method. The code is as Follows:</p></p><pre class="prettyprint"><code class="language-java hljs "><span class="hljs-annotation"><span class="hljs-annotation">@Override</span></span> <span class="hljs-keyword"><span class="hljs-keyword">protected</span></span> <span class="hljs-keyword"><span class="hljs-keyword">void</span></span> <span class="hljs-title"><span class="hljs-title">onCreate</span></span>(Bundle Savedinstancestate) {<span class="hljs-keyword"><span class="hljs-keyword">Super</span></span>. onCreate (savedinstancestate); Setcontentview (r.layout.activity_main); System.out.println (<span class="hljs-string"><span class="hljs-string">"first onCreate"</span></span>); }<span class="hljs-annotation"><span class="hljs-annotation">@Override</span></span> <span class="hljs-keyword"><span class="hljs-keyword">protected</span></span> <span class="hljs-keyword"><span class="hljs-keyword">void</span></span> <span class="hljs-title"><span class="hljs-title">OnStart</span></span>() {System.out.println (<span class="hljs-string"><span class="hljs-string">"first onStart"</span></span>);<span class="hljs-keyword"><span class="hljs-keyword">Super</span></span>. OnStart (); }<span class="hljs-annotation"><span class="hljs-annotation">@Override</span></span> <span class="hljs-keyword"><span class="hljs-keyword">protected</span></span> <span class="hljs-keyword"><span class="hljs-keyword">void</span></span> <span class="hljs-title"><span class="hljs-title">Onresume</span></span>() {System.out.println (<span class="hljs-string"><span class="hljs-string">"first onresume"</span></span>);<span class="hljs-keyword"><span class="hljs-keyword">Super</span></span>. Onresume (); }<span class="hljs-annotation"><span class="hljs-annotation">@Override</span></span> <span class="hljs-keyword"><span class="hljs-keyword">protected</span></span> <span class="hljs-keyword"><span class="hljs-keyword">void</span></span> <span class="hljs-title"><span class="hljs-title">OnPause</span></span>() {System.out.println (<span class="hljs-string"><span class="hljs-string">"first onPause"</span></span>);<span class="hljs-keyword"><span class="hljs-keyword">Super</span></span>. OnPause (); }<span class="hljs-annotation"><span class="hljs-annotation">@Override</span></span> <span class="hljs-keyword"><span class="hljs-keyword">protected</span></span> <span class="hljs-keyword"><span class="hljs-keyword">void</span></span> <span class="hljs-title"><span class="hljs-title">OnStop</span></span>() {System.out.println (<span class="hljs-string"><span class="hljs-string">"first onStop"</span></span>);<span class="hljs-keyword"><span class="hljs-keyword">Super</span></span>. OnStop (); }<span class="hljs-annotation"><span class="hljs-annotation">@Override</span></span> <span class="hljs-keyword"><span class="hljs-keyword">protected</span></span> <span class="hljs-keyword"><span class="hljs-keyword">void</span></span> <span class="hljs-title"><span class="hljs-title">Onrestart</span></span>() {System.out.println (<span class="hljs-string"><span class="hljs-string">"fisrt onrestart!"</span></span>);<span class="hljs-keyword"><span class="hljs-keyword">Super</span></span>. Onrestart (); }<span class="hljs-annotation"><span class="hljs-annotation">@Override</span></span> <span class="hljs-keyword"><span class="hljs-keyword">protected</span></span> <span class="hljs-keyword"><span class="hljs-keyword">void</span></span> <span class="hljs-title"><span class="hljs-title">OnDestroy</span></span>() {System.out.println (<span class="hljs-string"><span class="hljs-string">"first ondestory!"</span></span>);<span class="hljs-keyword"><span class="hljs-keyword">Super</span></span>. OnDestroy (); }</code></pre><p><p>Now we start the activity for the first Time. discovery Output:</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs mathematica"><span class="hljs-keyword">First</span> onCreate<span class="hljs-keyword">First</span> onStart<span class="hljs-keyword">First</span> onResume</code></pre></pre><p><p>When we click Home to return to the main interface, the output is:</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs mathematica"><span class="hljs-keyword">First</span> onPause<span class="hljs-keyword">First</span> onStop</code></pre></pre><p><p>In the click program, go back to the program, output for</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs mathematica"><span class="hljs-keyword">First</span> onRestart<span class="hljs-keyword">First</span> onStart<span class="hljs-keyword">First</span> onResume</code></pre></pre><p><p>When you click back, the output is</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs nginx"><span class="hljs-title">First</span><span class="hljs-built_in">on</span><span class="hljs-built_in">on</span><span class="hljs-built_in">on</span>Destory</code></pre></pre><p><p>The above output can clearly see the start-up process, not much to Describe.</p></p>3. Multiple activity life cycle<p><p>The two activity is created here, respectively, first and second,2, in fact, are the Same.<br>We added a button to the first activity, and when you click the button, you use intent to jump to second,<br>Jump Code:</p></p><pre class="prettyprint"><code class="language-java hljs "> <span class="hljs-annotation"><span class="hljs-annotation">@Override</span></span> <span class="hljs-keyword"><span class="hljs-keyword">protected</span></span> <span class="hljs-keyword"><span class="hljs-keyword">void</span></span> <span class="hljs-title"><span class="hljs-title">onCreate</span></span>(Bundle Savedinstancestate) {<span class="hljs-keyword"><span class="hljs-keyword">Super</span></span>. onCreate (savedinstancestate); Setcontentview (r.layout.activity_main); System.out.println (<span class="hljs-string"><span class="hljs-string">"first onCreate"</span></span>); Button btn = (button) Findviewbyid (r.id.btn); Btn.setonclicklistener (<span class="hljs-keyword"><span class="hljs-keyword">New</span></span>Onclicklistener () {<span class="hljs-annotation"><span class="hljs-annotation">@Override</span></span> <span class="hljs-keyword"><span class="hljs-keyword"></span> public</span> <span class="hljs-keyword"><span class="hljs-keyword">void</span></span> <span class="hljs-title"><span class="hljs-title">OnClick</span></span>(View Arg0) {Intent Intent =<span class="hljs-keyword"><span class="hljs-keyword">New</span></span>Intent (); Intent.setclass (mainactivity.<span class="hljs-keyword"><span class="hljs-keyword"></span> this</span>, secondactivity.class); StartActivity (intent); } }); }</code></pre><p><p>How to add a button control is not Elaborated.<br>Below we launch the application, which goes into first Activity. According to 2, the output order should be:</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs livecodeserver"><span class="hljs-keyword">first</span> onCreate<span class="hljs-keyword">first</span> onStart<span class="hljs-keyword">first</span> onResume</code></pre></pre><p><p>Then we click on the button to jump to second activity and the output is:</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs livecodeserver"><span class="hljs-keyword">first</span> onPause<span class="hljs-keyword">second</span> onCreate<span class="hljs-keyword">second</span> onStart<span class="hljs-keyword">second</span> onResume<span class="hljs-keyword">first</span> onStop</code></pre></pre><p><p>At this time the activities for the second activity, so at this point home operation, and the same as Above.<br>If we click Back to return to, then the output is</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs livecodeserver"><span class="hljs-keyword">second</span> onPause<span class="hljs-keyword">first</span> onRestart<span class="hljs-keyword">first</span> onStart<span class="hljs-keyword">first</span> onResume<span class="hljs-keyword">second</span> onStop<span class="hljs-keyword">second</span> onDestory</code></pre></pre><p><p>At this time second activity has been destroy off, if re-enter is not the same as above, but re-create a new activity, jump to second activity again, the output is:</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs livecodeserver"><span class="hljs-keyword">first</span> onPause<span class="hljs-keyword">second</span> onCreate<span class="hljs-keyword">second</span> onStart<span class="hljs-keyword">second</span> onResume<span class="hljs-keyword">first</span> onStop</code></pre></pre>4. Summary<p><p>The above program output has put the order of the call, explained very clearly. We recommend that you overload those 7 functions, and then start it yourself, and experiment to increase the understanding.</p></p> <p><p>Life cycle of Android--activity (i.)</p></p></span>