Providing UP Navigation in Android

Step1: specifying parentActivityName attibute in an activity

Declare which activity is the appropriate parent for each activity. You can do it by specifying parentActivityName attibute in an activity.

<activity
 android:name="com.example.test.MainActivity2"
 android:label="@string/title_activity_main_activity2"
 android:parentActivityName="com.example.test.MainActivity" >
</activity>

Step2: Call setDisplayHomeAsUpEnabled() method of getActionBar() in the onCreate()

Call setDisplayHomeAsUpEnabled() method of getActionBar() in the onCreate method of the activity to enable the back button in the top action bar

@Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main_activity2);
      getActionBar().setDisplayHomeAsUpEnabled(true);
   }

Step3: Override onOptionsItemSelected()

When the user presses it, your activity receives a call to onOptionsItemSelected(). The ID for the action is android.R.id.home.

public boolean onOptionsItemSelected(MenuItem item) {
 switch (item.getItemId()) {
  case android.R.id.home:
  NavUtils.navigateUpFromSameTask(this);
  return true;
 } 
}

Step4: Handling device back button

Overrid onBackPressed() and then calling moveTaskToBack() and finish() method.

@Override
public void onBackPressed() {
   moveTaskToBack(true); 
   MainActivity2.this.finish();
}

Complete Code:

<application
      android:allowBackup="true"
      android:icon="@drawable/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme" >
      <activity
         android:name="com.example.test.MainActivity"
         android:label="@string/app_name" >
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
      <activity
         android:name="com.example.test.MainActivity2"
         android:label="@string/title_activity_main_activity2"
         android:parentActivityName="com.example.test.MainActivity" >
      </activity>
   </application>

public class MainActivity2 extends Activity {

   @SuppressLint("NewApi")
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main_activity2);
      getActionBar().setDisplayHomeAsUpEnabled(true);
   }
   @Override
   public boolean onCreateOptionsMenu(Menu menu) {
      // Inflate the menu; this adds items to the action bar if it is present.
      getMenuInflater().inflate(R.menu.main_activity2, menu);
      return true;
   }  
   @Override
   public boolean onOptionsItemSelected(MenuItem item) {
      switch (item.getItemId()) {
         // Respond to the action bar's Up/Home button
         case android.R.id.home:
         NavUtils.navigateUpFromSameTask(this);
         return true;
      }
      return super.onOptionsItemSelected(item);
   }
   @Override
   public void onBackPressed() {
      moveTaskToBack(true); 
      MainActivity2.this.finish();
   }

}

Next Article: Android - Sending data from one activity to another

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