guide/components/activities.jd

page.title=
page.tags=activity,intent
@jd:body

<div id="qv-wrapper">
<div id="qv">
<h2></h2>
<ol>
  <li><a href="#Creating"></a>
    <ol>
      <li><a href="#UI"> </a></li>
      <li><a href="#Declaring"></a></li>
    </ol>
  </li>
  <li><a href="#StartingAnActivity"></a>
    <ol>
      <li><a href="#StartingAnActivityForResult"></a></li>
    </ol>
  </li>
  <li><a href="#ShuttingDown"></a></li>
  <li><a href="#Lifecycle"></a>
    <ol>
      <li><a href="#ImplementingLifecycleCallbacks"> </a></li>
      <li><a href="#SavingActivityState"></a></li>
      <li><a href="#ConfigurationChanges"></a></li>
      <li><a href="#CoordinatingActivities"></a></li>
    </ol>
  </li>
</ol>

<h2></h2>
<ol>
  <li>{@link android.app.Activity}</li>
</ol>

<h2></h2>
<ol>
  <li><a href="{@docRoot}guide/components/tasks-and-back-stack.html">
</a></li>
</ol>

</div>
</div>


<p>{@link android.app.Activity}


</p>

<p>
 1


  [<em></em>]

<a href="{@docRoot}guide/components/tasks-and-back-stack.html"></a>

</p>

<p>


&mdash;&mdash;


</p>

<p>

</p>


<h2 id="Creating"></h2>

<p>{@link android.app.Activity}


  2
</p>

<dl>
  <dt>{@link android.app.Activity#onCreate onCreate()}</dt>
  <dd>


     {@link android.app.Activity#setContentView
    setContentView()}  </dd>
  <dt>{@link android.app.Activity#onPause onPause()}</dt>
  <dd>


</dd>
</dl>

<p>

  <a href="#Lifecycle"></a>
</p>


<h3 id="UI"> </h3>

<p>   {@link android.view.View} &mdash;

1
</p>

<p>Android

{@link
android.view.ViewGroup}
{@link android.view.View}  {@link android.view.ViewGroup}

</p>

<p>XML

{@link android.app.Activity#setContentView(int) setContentView()}  ID  UI

  {@link android.view.View} {@link android.view.ViewGroup}  {@link
android.view.View}  {@link android.view.ViewGroup}  {@link android.app.Activity#setContentView(View)
setContentView()}

</p>

<p> <a href="{@docRoot}guide/topics/ui/index.html"> </a></p>


<h3 id="Declaring"></h3>

<p>
 <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity&gt;}</a>  <a href="{@docRoot}guide/topics/manifest/application-element.html">{@code &lt;application&gt;}</a>

</p>

<pre>
&lt;manifest ... &gt;
  &lt;application ... &gt;
      &lt;activity android:name=".ExampleActivity" /&gt;
      ...
  &lt;/application ... &gt;
  ...
&lt;/manifest &gt;
</pre>

<p> UI <a href="{@docRoot}guide/topics/manifest/activity-element.html#nm">{@code android:name}</a>


&mdash;<a href="http://android-developers.blogspot.com/2011/06/things-that-cannot-change.html">Things That Cannot Change</a>


</p>

<p><a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity&gt;}</a>
</p>


<h4> </h4>

<p><a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code
&lt;activity&gt;}</a>  &mdash; <a href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code
&lt;intent-filter&gt;}</a>   &mdash;
</p>

<p>Android SDK


</p>

<pre>
&lt;activity android:name=".ExampleActivity" android:icon="@drawable/app_icon"&gt;
    &lt;intent-filter&gt;
        &lt;action android:name="android.intent.action.MAIN" /&gt;
        &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
    &lt;/intent-filter&gt;
&lt;/activity&gt;
</pre>

<p><a href="{@docRoot}guide/topics/manifest/action-element.html">{@code
&lt;action&gt;}</a>  <a href="{@docRoot}guide/topics/manifest/category-element.html">{@code
&lt;category&gt;}</a>
</p>

<p>
 1


</p>

<p>

<a href="{@docRoot}guide/topics/manifest/action-element.html">{@code
&lt;action&gt;}</a>  <a href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code
&lt;intent-filter&gt;}</a>  <a href="{@docRoot}guide/topics/manifest/category-element.html">{@code
&lt;category&gt;}</a>  <a href="{@docRoot}guide/topics/manifest/data-element.html">{@code
&lt;data&gt;}</a>

</p>

<p><a href="{@docRoot}guide/components/intents-filters.html"> </a>
</p>


<h2 id="StartingAnActivity"></h2>

<p>@link android.app.Activity#startActivity
  startActivity()}  {@link android.content.Intent}


</p>

<p>

1  {@code
SignInActivity} </p>

<pre>
Intent intent = new Intent(this, SignInActivity.class);
startActivity(intent);
</pre>

<p>


&mdash;

 1


</p>

<pre>
Intent intent = new Intent(Intent.ACTION_SEND);
intent.putExtra(Intent.EXTRA_EMAIL, recipientArray);
startActivity(intent);
</pre>

<p> {@link android.content.Intent#EXTRA_EMAIL}


</p>


<h3 id="StartingAnActivityForResult"></h3>

<p>{@link android.app.Activity#startActivityForResult
  startActivityForResult()}{@link android.app.Activity#startActivity
  startActivity()}

{@link android.app.Activity#onActivityResult onActivityResult()}
{@link
android.content.Intent}  {@link android.app.Activity#onActivityResult onActivityResult()}
</p>

<p> 1

</p>

<pre>
private void pickContact() {
    // Create an intent to "pick" a contact, as defined by the content provider URI
    Intent intent = new Intent(Intent.ACTION_PICK, Contacts.CONTENT_URI);
    startActivityForResult(intent, PICK_CONTACT_REQUEST);
}

&#64;Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // If the request went well (OK) and the request was PICK_CONTACT_REQUEST
    if (resultCode == Activity.RESULT_OK &amp;&amp; requestCode == PICK_CONTACT_REQUEST) {
        // Perform a query to the contact's content provider for the contact's name
        Cursor cursor = getContentResolver().query(data.getData(),
        new String[] {Contacts.DISPLAY_NAME}, null, null, null);
        if (cursor.moveToFirst()) { // True if the cursor is not empty
            int columnIndex = cursor.getColumnIndex(Contacts.DISPLAY_NAME);
            String name = cursor.getString(columnIndex);
            // Do something with the selected contact's name...
        }
    }
}
</pre>

<p> {@link
android.app.Activity#onActivityResult onActivityResult()}
1  {@code resultCode} {@link android.app.Activity#RESULT_OK} {@code requestCode}  {@link android.app.Activity#startActivityForResult
startActivityForResult()}  2 &mdash;
&mdash;&mdash;

 {@link android.content.Intent}{@code data}
</p>

<p>{@link
android.content.ContentResolver}   {@link android.database.Cursor}
<a href="{@docRoot}guide/topics/providers/content-providers.html"> </a>
</p>

<p><a href="{@docRoot}guide/components/intents-filters.html"> </a>
</p>


<h2 id="ShuttingDown"></h2>

<p>{@link android.app.Activity#finish
finish()} {@link android.app.Activity#finishActivity finishActivity()}
</p>

<p class="note"><strong>:</strong>
Android


</p>


<h2 id="Lifecycle"></h2>

<p>


</p>

<p> 3 </p>

<dl>
  <dt><i></i></dt>
    <dd>
</dd>

  <dt><i></i></dt>
    <dd>

{@link android.app.Activity}

</dd>

  <dt><i></i></dt>
    <dd>
{@link android.app.Activity}  <em></em>


</dd>
</dl>

<p>{@link android.app.Activity#finish finish()}


</p>


<h3 id="ImplementingLifecycleCallbacks"> </h3>

<p>


</p>


<pre>
public class ExampleActivity extends Activity {
    &#64;Override
    public void {@link android.app.Activity#onCreate onCreate}(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // The activity is being created.
    }
    &#64;Override
    protected void {@link android.app.Activity#onStart onStart()} {
        super.onStart();
        // The activity is about to become visible.
    }
    &#64;Override
    protected void {@link android.app.Activity#onResume onResume()} {
        super.onResume();
        // The activity has become visible (it is now "resumed").
    }
    &#64;Override
    protected void {@link android.app.Activity#onPause onPause()} {
        super.onPause();
        // Another activity is taking focus (this activity is about to be "paused").
    }
    &#64;Override
    protected void {@link android.app.Activity#onStop onStop()} {
        super.onStop();
        // The activity is no longer visible (it is now "stopped")
    }
    &#64;Override
    protected void {@link android.app.Activity#onDestroy onDestroy()} {
        super.onDestroy();
        // The activity is about to be destroyed.
    }
}
</pre>

<p class="note"><strong>:</strong>
</p>

<p> 3
 </p>

<ul>
<li><b> entire lifetime</b> {@link
android.app.Activity#onCreate onCreate()} {@link
android.app.Activity#onDestroy} {@link android.app.Activity#onCreate onCreate()} {@link android.app.Activity#onDestroy}

 {@link android.app.Activity#onCreate onCreate()} {@link
android.app.Activity#onDestroy}

</li>

<li><p><b>visible lifetime</b> {@link
android.app.Activity#onStart onStart()} {@link
android.app.Activity#onStop onStop()}
 {@link android.app.Activity#onStop onStop()}
 2
{@link android.content.BroadcastReceiver}  {@link
android.app.Activity#onStart onStart()}  UI  {@link android.app.Activity#onStop onStop()}


 entire lifetime  {@link android.app.Activity#onStart onStart()}  {@link
android.app.Activity#onStop onStop()}
</p></li>

<li><p> <b>foreground lifetime</b>  {@link
android.app.Activity#onResume onResume()} {@link android.app.Activity#onPause
onPause()}
 {@link android.app.Activity#onPause onPause()}
&mdash;
 2
</p></li>
</ul>

<p> 1

 <p>

<img src="{@docRoot}images/activity_lifecycle.png" alt="" />
<p class="img-caption"><strong> 1.</strong> </p>

<p> 1


</p>

<p class="table-caption"><strong> 1.</strong>
</p>

<table border="2" width="85%" frame="hsides" rules="rows">
<colgroup align="left" span="3"></colgroup>
<colgroup align="left"></colgroup>
<colgroup align="center"></colgroup>
<colgroup align="center"></colgroup>

<thead>
<tr><th colspan="3"></th> <th></th> <th></th> <th></th></tr>
</thead>

<tbody>
<tr>
  <td colspan="3" align="left"><code>{@link android.app.Activity#onCreate onCreate()}</code></td>
  <td>
      &mdash;
 Bundle <a href="#actstate"></a>


      <p> {@code onStart()} </p></td>
  <td align="center"></td>
      <td align="center">{@code onStart()}</td>
</tr>

<tr>
   <td rowspan="5" style="border-left: none; border-right: none;">&nbsp;&nbsp;&nbsp;&nbsp;</td>
   <td colspan="2" align="left"><code>{@link android.app.Activity#onRestart
onRestart()}</code></td>
   <td>

       <p> {@code onStart()} </p></td>
   <td align="center"></td>
   <td align="center">{@code onStart()}</td>
</tr>

<tr>
   <td colspan="2" align="left"><code>{@link android.app.Activity#onStart onStart()}</code></td>
   <td>
       <p> {@code onResume()}  {@code onStop()}
</p></td>
    <td align="center"></td>
    <td align="center">{@code onResume()} <br/><br/> {@code onStop()}</td>
</tr>

<tr>
   <td rowspan="2" style="border-left: none;">&nbsp;&nbsp;&nbsp;&nbsp;</td>
   <td align="left"><code>{@link android.app.Activity#onResume onResume()}</code></td>
   <td>


       <p> {@code onPause()} </p></td>
   <td align="center"></td>
   <td align="center">{@code onPause()}</td>
</tr>

<tr>
   <td align="left"><code>{@link android.app.Activity#onPause onPause()}</code></td>
   <td>
 CPU


       <p> {@code onResume()}  {@code onStop()}

</td>
   <td align="center"><strong style="color:#800000"></strong></td>
   <td align="center">{@code onResume()} <br/><br/> {@code onStop()}</td>
</tr>

<tr>
   <td colspan="2" align="left"><code>{@link android.app.Activity#onStop onStop()}</code></td>
   <td>


       <p> {@code onRestart()}  {@code onDestroy()}

</p></td>
   <td align="center"><strong style="color:#800000"></strong></td>
   <td align="center">{@code onRestart()} <br/><br/> {@code onDestroy()}</td>
</tr>

<tr>
   <td colspan="3" align="left"><code>{@link android.app.Activity#onDestroy
onDestroy()}</code></td>
   <td>
<code>{@link android.app.Activity#finish
       finish()}</code>

 2 <code>{@link
       android.app.Activity#isFinishing isFinishing()}</code>
</td>
   <td align="center"><strong style="color:#800000"></strong></td>
   <td align="center"><em></em></td>
</tr>
</tbody>
</table>

<p><em></em>

3 {@link
android.app.Activity#onPause
onPause()}{@link android.app.Activity#onStop onStop()}{@link android.app.Activity#onDestroy
onDestroy()}{@link android.app.Activity#onPause onPause()}  3 {@link android.app.Activity#onPause onPause()} <em></em>{@link
android.app.Activity#onStop onStop()}  {@link android.app.Activity#onDestroy onDestroy()}

&mdash;

{@link android.app.Activity#onPause onPause()}
{@link android.app.Activity#onPause onPause()}


</p>

<p> <b></b>
{@link android.app.Activity#onPause onPause()} {@link android.app.Activity#onResume onResume()}

{@link android.app.Activity#onPause onPause()}
 </p>

<p class="note"><strong>:</strong>  1
&mdash;
<a href="{@docRoot}guide/components/processes-and-threads.html">Processes and Threading</a>

</p>


<h3 id="SavingActivityState"></h3>

<p><a href="#Lifecycle"></a>

 {@link android.app.Activity}  &mdash;


</p>

<p> {@link
android.app.Activity}
 {@link android.app.Activity}


 {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()}

</p>

<p> {@link android.app.Activity#onSaveInstanceState onSaveInstanceState()}
 {@link android.os.Bundle}  {@link
android.os.Bundle#putString putString()}  {@link
android.os.Bundle#putInt putInt()}

  {@link android.os.Bundle}  {@link android.app.Activity#onCreate onCreate()}  {@link
android.app.Activity#onRestoreInstanceState onRestoreInstanceState()}

 {@link android.os.Bundle}

{@link
android.os.Bundle}  null
</p>

<img src="{@docRoot}images/fundamentals/restore_instance.png" alt="" />
<p class="img-caption"><strong> 2.</strong>   2


</p>

<p class="note"><strong>:</strong>  {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()}  [<em></em>]


 {@link android.app.Activity#onSaveInstanceState
onSaveInstanceState()}  {@link
android.app.Activity#onStop onStop()}  {@link android.app.Activity#onPause
onPause()} </p>

<p> {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()} {@link android.app.Activity}  {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()}
 {@link
android.view.View}  {@link
android.view.View#onSaveInstanceState onSaveInstanceState()}

Android UI

{@link android.widget.EditText} {@link android.widget.CheckBox}

 ID<a href="{@docRoot}guide/topics/resources/layout-resource.html#idvalue">{@code android:id}</a>
 ID
</p>

<div class="sidebox-wrapper">
<div class="sidebox">
<p>{@link android.R.attr#saveEnabled android:saveEnabled}  {@code "false"} {@link android.view.View#setSaveEnabled setSaveEnabled()}

 UI
</p>
</div>
</div>

<p>{@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()}  UI UI  UI


</p>

<p>{@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()}  UI  {@link android.app.Activity#onSaveInstanceState onSaveInstanceState()}


{@link
android.app.Activity#onRestoreInstanceState onRestoreInstanceState()}
</p>

<p class="note"><strong>:</strong> {@link android.app.Activity#onSaveInstanceState
onSaveInstanceState()}

&mdash; {@link
android.app.Activity#onPause onPause()}
</p>

<p>


</p>


<h3 id="ConfigurationChanges"></h3>

<p>
Android  {@link android.app.Activity#onDestroy}  {@link
android.app.Activity#onCreate onCreate()}


</p>

<p>

</p>

<p>{@link
  android.app.Activity#onSaveInstanceState onSaveInstanceState()}  {@link
android.app.Activity#onRestoreInstanceState onRestoreInstanceState()} {@link
android.app.Activity#onCreate onCreate()}
</p>

<p><a href="{@docRoot}guide/topics/resources/runtime-changes.html"></a>

</p>


<h3 id="CoordinatingActivities"></h3>

 <p>1 1

2  1 2 1


</p>

<p> 2  1
 A  B
 </p>

<ol>
<li> A  {@link android.app.Activity#onPause onPause()} </li>

<li> B  {@link android.app.Activity#onCreate onCreate()}{@link
android.app.Activity#onStart onStart()}{@link android.app.Activity#onResume onResume()}
  B </li>

<li> A {@link
android.app.Activity#onStop onStop()} </li>
</ol>

 <p> 1
1  {@link
android.app.Activity#onStop onStop()}  {@link android.app.Activity#onPause onPause()}

</p>

<!--
<h2>Beginner's Path</h2>

<p>For more information about how Android maintains a history of activities and
enables user multitasking, continue with the <b><a
href="{@docRoot}guide/components/tasks-and-back-stack.html">Tasks and Back
Stack</a></b> document.</p>
-->