android-fragments Getting started with android-fragments
Remarks
Fragments are very important components of user interface in android apps. They were introduced first in Android 3.0 (Honeycomb) API.
Understanding design paradigm of Fragments
Fragments were introduced for primarily supporting modular and flexible UI on large screen devices such as tablets.
Fragments are managed by an activity. Usually each fragment represents a portion of a screen. There can be more than one fragment in an activity. Fragments may also be called sub-activities. When you add a fragment as a part of your activity layout, it lives in a ViewGroup inside the activity's view hierarchy and the fragment defines its own view layout.
LIFECYCLE
Just like an activities, fragments also have a lifecycle. A fragment gets notified for following events.
- Get attached to activity - onAttach(Activity)
- Create fragment - onCreate(Bundle)
- Create View - onCreateView(LayoutInflater, ViewGroup, Bundle)
- Activity creation - onActivityCreated(Bundle)
- View state restored - onViewStateRestored(Bundle)
- Made visible to user - onStart()
- start of user interaction - onResume()
- pause of user interaction - onPause()
- Made invisible to user - onStop()
- On view destruction - onDestroyView()
- Destroy fragment - onDestroy()
- Get detached from an activity - onDetach()
As a programmer, you should override various lifecycle callback methods, typically we implement onCreate(), onCreateView() and onPause() methods.
Subclasses of Fragment
- DialogFragment - For displaying the floating dialog
- ListFragment - For displaying list of items
- PreferenceFragment - Useful for creating settings activity
References
Adding Fragments
Adding a Fragment Statically
File: activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<fragment
android:id="@+id/fragment2"
android:name="com.example.fragmentexample.Fragment2"
android:layout_width="0px"
android:layout_height="match_parent"
android:layout_weight="1"
/>
<fragment
android:id="@+id/fragment1"
android:name="com.example.fragmentexample.Fragment1"
android:layout_width="0px"
android:layout_height="match_parent"
android:layout_weight="1"
/>
</LinearLayout>
File: fragment1.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="#00ff00"
>
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="fragment frist"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
File: fragment2.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="#0000ff"
>
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Second Fragment"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
File: MainActivity.java
package com.example.fragmentexample;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
File: Fragment1.java
package com.example.fragmentexample;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class Fragment1 extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
return inflater.inflate(R.layout.fragment1,container, false);
}
}
File: Fragment2.java
package com.example.fragmentexample;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class Fragment2 extends Fragment {
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
return inflater.inflate(R.layout.fragment2,container, false);
}
}
Adding a Fragment Dynamically
activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<FrameLayout
android:id="@+id/container1"
android:layout_width="0px"
android:layout_height="match_parent"
android:layout_weight="1"
/>
<FrameLayout
android:id="@+id/container2"
android:layout_width="0px"
android:layout_height="match_parent"
android:layout_weight="1"
/>
</LinearLayout>
FrameLayout is acting as fragment container.
MainActivity class
File: MainActivity.java
package com.example.fragmentexample;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
loadFragment(this, R.id.container1,new Fragment1(),"fragment1");
loadFragment(this, R.id.container2,new Fragment2(),"fragment2");
}
public static void loadFragment(Activity activity, int containerId, Fragment fragment, String tag)
{
activity.getSupportFragmentManager().beginTransaction().
replace(containerId, fragment,tag).commitAllowingStateLoss();
}
}
