title: Android, bring already started activity back to front
body: <p>My android application has multiple activities. Each activity has a 'Back to Home' button. For example, Main activity opens sub-activity A, sub-activity A opens sub-activity B.</p>
  
  <p>On the screen of sub-activity B, there's a 'Back to Home' button which is supposed to bring back the Main activity into visibility.</p>
  
  <p>I've tried the flag <strong>Intent.FLAG_ACTIVITY_REORDER_TO_FRONT</strong> but no use.</p>
  
  <p>This is a part of my AndroidManifest.xml:</p>
  
  <pre><code>...
  &lt;activity android:name="vn.agritrade.Main_Activity"
  android:label="Agritrade"
  android:screenOrientation="portrait"
  android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
  android:uiOptions="splitActionBarWhenNarrow"
  android:launchMode="singleInstance"&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;
  ...
  </code></pre>
  
  <p>This is how I relaunch the Main activity:</p>
  
  <pre><code>/**
   * Relaunch main activity (called by 'Back to Home' button)
   */
  public void open_main_activity(View view) {
    Intent intent = new Intent(this,Main_Activity.class);
    intent.putExtra(DEFAULT_EXTRA,"");
    intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
    startActivity(intent);    
  }
  </code></pre>
  
  <p>What else should I need?</p>