Fragment

Default constructor. Every fragment must have an empty constructor, so it can be instantiated when restoring its activity's state. It is strongly recommended that subclasses do not have other constructors with parameters, since these constructors will not be called when the fragment is re-instantiated; instead, arguments can be supplied by the caller with setArguments(Bundle) and later retrieved by the Fragment with getArguments().

Applications should generally not implement a constructor. The first place application code an run where the fragment is ready to be used is in onAttach(Activity), the point where the fragment is actually associated with its activity. Some applications may also want to implement onInflate(Activity, AttributeSet, Bundle) to retrieve attributes from a layout resource, though should take care here because this happens for the fragment is attached to its activity.

Print the Fragments's state into the given stream.

Subclasses can not override equals().

Return the Activity this fragment is currently associated with.

Return the arguments supplied when the fragment was instantiated, if any.

Return the FragmentManager for interacting with fragments associated with this fragment's activity. Note that this will be non-null slightly before getActivity(), during the time from when the fragment is placed in a FragmentTransaction until it is committed and attached to its activity.

Return the identifier this fragment is known by. This is either the android:id value supplied in a layout or the container view ID supplied when adding the fragment.

Return the LoaderManager for this fragment, creating it if needed.

Return getActivity().getResources().

Return a localized string from the application's package's default string table.

Return a localized formatted string from the application's package's default string table, substituting the format arguments as defined in Formatter and format(String, Object...).

Get the tag name of the fragment, if specified.

Return the target fragment set by setTargetFragment(Fragment, int).

Return the target request code set by setTargetFragment(Fragment, int).

Return a localized, styled CharSequence from the application's package's default string table.

Get the root view for the fragment's layout (the one returned by onCreateView(LayoutInflater, ViewGroup, Bundle)), if provided.

Subclasses can not override hashCode().

Like instantiate(Context, String, Bundle) but with a null argument Bundle.

Create a new instance of a Fragment with the given class name. This is the same as calling its empty constructor.

Return true if the fragment is currently added to its activity.

Return true if the fragment has been explicitly detached from the UI. That is, FragmentTransaction.detach(Fragment) has been used on it.

Return true if the fragment has been hidden. By default fragments are shown. You can find out about changes to this state with onHiddenChanged(boolean). Note that the hidden state is orthogonal to other states -- that is, to be visible to the user, a fragment must be both started and not hidden.

Return true if the layout is included as part of an activity view hierarchy via the <fragment> tag. This will always be true when fragments are created through the <fragment> tag, except in the case where an old fragment is restored from a previous state and it does not appear in the layout of the current state.

Return true if this fragment is currently being removed from its activity. This is not whether its activity is finishing, but rather whether it is in the process of being removed from its activity.

Return true if the fragment is in the resumed state. This is true for the duration of onResume() and onPause() as well.

Return true if the fragment is currently visible to the user. This means it: (1) has been added, (2) has its view attached to the window, and (3) is not hidden.

Called when the fragment's activity has been created and this fragment's view hierarchy instantiated. It can be used to do final initialization once these pieces are in place, such as retrieving views or restoring state. It is also useful for fragments that use setRetainInstance(boolean) to retain their instance, as this callback tells the fragment when it is fully associated with the new activity instance. This is called after onCreateView(LayoutInflater, ViewGroup, Bundle) and before onStart().

Receive the result from a previous call to startActivityForResult(Intent, int). This follows the related Activity API as described there in onActivityResult(int, int, Intent).

Called when a fragment is first attached to its activity. onCreate(Bundle) will be called after this.

Called by the system when the device configuration changes while your component is running. Note that, unlike activities, other components are never restarted when a configuration changes: they must always deal with the results of the change, such as by re-retrieving resources.

At the time that this function has been called, your Resources object will have been updated to return resource values matching the new configuration.

This hook is called whenever an item in a context menu is selected. The default implementation simply returns false to have the normal processing happen (calling the item's Runnable or sending a message to its Handler as appropriate). You can use this method for any items for which you would like to do processing without those other facilities.

Use getMenuInfo() to get extra information set by the View that added this menu item.

Derived classes should call through to the base class for it to perform the default menu handling.

Called to do initial creation of a fragment. This is called after onAttach(Activity) and before onCreateView(LayoutInflater, ViewGroup, Bundle).

Note that this can be called while the fragment's activity is still in the process of being created. As such, you can not rely on things like the activity's content view hierarchy being initialized at this point. If you want to do work once the activity itself is created, see onActivityCreated(Bundle).

Called when a fragment loads an animation.

Called when a context menu for the view is about to be shown. Unlike onCreateOptionsMenu(Menu, MenuInflater), this will be called every time the context menu is about to be shown and should be populated for the view (or item inside the view for AdapterView subclasses, this can be found in the menuInfo)).

Use onContextItemSelected(android.view.MenuItem) to know when an item has been selected.

The default implementation calls up to Activity.onCreateContextMenu, though you can not call this implementation if you don't want that behavior.

It is not safe to hold onto the context menu after this method returns. Called when the context menu for this view is being built. It is not safe to hold onto the menu after this method returns.

Initialize the contents of the Activity's standard options menu. You should place your menu items in to menu. For this method to be called, you must have first called setHasOptionsMenu(boolean). See Activity.onCreateOptionsMenu for more information.

Called to have the fragment instantiate its user interface view. This is optional, and non-graphical fragments can return null (which is the default implementation). This will be called between onCreate(Bundle) and onActivityCreated(Bundle).

If you return a View from here, you will later be called in onDestroyView() when the view is being released.

Called when the fragment is no longer in use. This is called after onStop() and before onDetach().

Called when this fragment's option menu items are no longer being included in the overall options menu. Receiving this call means that the menu needed to be rebuilt, but this fragment's items were not included in the newly built menu (its onCreateOptionsMenu(Menu, MenuInflater) was not called).

Called when the view previously created by onCreateView(LayoutInflater, ViewGroup, Bundle) has been detached from the fragment. The next time the fragment needs to be displayed, a new view will be created. This is called after onStop() and before onDestroy(). It is called regardless of whether onCreateView(LayoutInflater, ViewGroup, Bundle) returned a non-null view. Internally it is called after the view's state has been saved but before it has been removed from its parent.

Called when the fragment is no longer attached to its activity. This is called after onDestroy().

Called when the hidden state (as returned by isHidden() of the fragment has changed. Fragments start out not hidden; this will be called whenever the fragment changes state from that.

Called when a fragment is being created as part of a view layout inflation, typically from setting the content view of an activity. This may be called immediately after the fragment is created from a tag in a layout file. Note this is before the fragment's onAttach(Activity) has been called; all you should do here is parse the attributes and save them away.

This is called every time the fragment is inflated, even if it is being inflated into a new instance with saved state. It typically makes sense to re-parse the parameters each time, to allow them to change with different configurations.

Here is a typical implementation of a fragment that can take parameters both through attributes supplied here as well from getArguments():

public static class MyFragment extends Fragment {
    CharSequence mLabel;

    /**
     * Create a new instance of MyFragment that will be initialized
     * with the given arguments.
     */
    static MyFragment newInstance(CharSequence label) {
        MyFragment f = new MyFragment();
        Bundle b = new Bundle();
        b.putCharSequence("label", label);
        f.setArguments(b);
        return f;
    }

    /**
     * Parse attributes during inflation from a view hierarchy into the
     * arguments we handle.
     */
    @Override public void onInflate(Activity activity, AttributeSet attrs,
            Bundle savedInstanceState) {
        super.onInflate(activity, attrs, savedInstanceState);

        TypedArray a = activity.obtainStyledAttributes(attrs,
                R.styleable.FragmentArguments);
        mLabel = a.getText(R.styleable.FragmentArguments_android_label);
        a.recycle();
    }

    /**
     * During creation, if arguments have been supplied to the fragment
     * then parse those out.
     */
    @Override public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Bundle args = getArguments();
        if (args != null) {
            mLabel = args.getCharSequence("label", mLabel);
        }
    }

    /**
     * Create the view for this fragment, using the arguments given to it.
     */
    @Override public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.hello_world, container, false);
        View tv = v.findViewById(R.id.text);
        ((TextView)tv).setText(mLabel != null ? mLabel : "(no label)");
        tv.setBackgroundDrawable(getResources().getDrawable(android.R.drawable.gallery_thumb));
        return v;
    }
}

Note that parsing the XML attributes uses a "styleable" resource. The declaration for the styleable used here is:

<declare-styleable name="FragmentArguments">
    <attr name="android:label" />
</declare-styleable>

The fragment can then be declared within its activity's content layout through a tag like this:

<fragment class="com.example.android.apis.app.FragmentArguments$MyFragment"
        android:id="@+id/embedded"
        android:layout_width="0px" android:layout_height="wrap_content"
        android:layout_weight="1"
        android:label="@string/fragment_arguments_embedded" />

This fragment can also be created dynamically from arguments given at runtime in the arguments Bundle; here is an example of doing so at creation of the containing activity:

@Override protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.fragment_arguments);

    if (savedInstanceState == null) {
        // First-time init; create fragment to embed in activity.
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        Fragment newFragment = MyFragment.newInstance("From Arguments");
        ft.add(R.id.created, newFragment);
        ft.commit();
    }
}

This is called when the overall system is running low on memory, and would like actively running process to try to tighten their belt. While the exact point at which this will be called is not defined, generally it will happen around the time all background process have been killed, that is before reaching the point of killing processes hosting service and foreground UI that we would like to avoid killing.

Applications that want to be nice can implement this method to release any caches or other unnecessary resources they may be holding on to. The system will perform a gc for you after returning from this method.

This hook is called whenever an item in your options menu is selected. The default implementation simply returns false to have the normal processing happen (calling the item's Runnable or sending a message to its Handler as appropriate). You can use this method for any items for which you would like to do processing without those other facilities.

Derived classes should call through to the base class for it to perform the default menu handling.

This hook is called whenever the options menu is being closed (either by the user canceling the menu with the back/menu button, or when an item is selected).

Called when the Fragment is no longer resumed. This is generally tied to Activity.onPause of the containing Activity's lifecycle.

Prepare the Screen's standard options menu to be displayed. This is called right before the menu is shown, every time it is shown. You can use this method to efficiently enable/disable items or otherwise dynamically modify the contents. See Activity.onPrepareOptionsMenu for more information.

Called when the fragment is visible to the user and actively running. This is generally tied to Activity.onResume of the containing Activity's lifecycle.

Called to ask the fragment to save its current dynamic state, so it can later be reconstructed in a new instance of its process is restarted. If a new instance of the fragment later needs to be created, the data you place in the Bundle here will be available in the Bundle given to onCreate(Bundle), onCreateView(LayoutInflater, ViewGroup, Bundle), and onActivityCreated(Bundle).

This corresponds to Activity.onSaveInstanceState(Bundle) and most of the discussion there applies here as well. Note however: this method may be called at any time before onDestroy(). There are many situations where a fragment may be mostly torn down (such as when placed on the back stack with no UI showing), but its state will not be saved until its owning activity actually needs to save its state.

Called when the Fragment is visible to the user. This is generally tied to Activity.onStart of the containing Activity's lifecycle.

Called when the Fragment is no longer started. This is generally tied to Activity.onStop of the containing Activity's lifecycle.

Called when the operating system has determined that it is a good time for a process to trim unneeded memory from its process. This will happen for example when it goes in the background and there is not enough memory to keep as many background processes running as desired. You should never compare to exact values of the level, since new intermediate values may be added -- you will typically want to compare if the value is greater or equal to a level you are interested in.

To retrieve the processes current trim level at any point, you can use ActivityManager.getMyMemoryState(RunningAppProcessInfo).

Called immediately after onCreateView(LayoutInflater, ViewGroup, Bundle) has returned, but before any saved state has been restored in to the view. This gives subclasses a chance to initialize themselves once they know their view hierarchy has been completely created. The fragment's view hierarchy is not however attached to its parent at this point.

Registers a context menu to be shown for the given view (multiple views can show the context menu). This method will set the View.OnCreateContextMenuListener on the view to this fragment, so onCreateContextMenu(ContextMenu, View, ContextMenuInfo) will be called when it is time to show the context menu.

Supply the construction arguments for this fragment. This can only be called before the fragment has been attached to its activity; that is, you should call it immediately after constructing the fragment. The arguments supplied here will be retained across fragment destroy and creation.

Report that this fragment would like to participate in populating the options menu by receiving a call to onCreateOptionsMenu(Menu, MenuInflater) and related methods.

Set the initial saved state that this Fragment should restore itself from when first being constructed, as returned by FragmentManager.saveFragmentInstanceState.

Set a hint for whether this fragment's menu should be visible. This is useful if you know that a fragment has been placed in your view hierarchy so that the user can not currently seen it, so any menu items it has should also not be shown.

Control whether a fragment instance is retained across Activity re-creation (such as from a configuration change). This can only be used with fragments not in the back stack. If set, the fragment lifecycle will be slightly different when an activity is recreated:

• onDestroy() will not be called (but onDetach() still will be, because the fragment is being detached from its current activity).
• onCreate(Bundle) will not be called since the fragment is not being re-created.
• onAttach(Activity) and onActivityCreated(Bundle) will still be called.

Optional target for this fragment. This may be used, for example, if this fragment is being started by another, and when done wants to give a result back to the first. The target set here is retained across instances via FragmentManager.putFragment().

Set a hint to the system about whether this fragment's UI is currently visible to the user. This hint defaults to true and is persistent across fragment instance state save and restore.

An app may set this to false to indicate that the fragment's UI is scrolled out of visibility or is otherwise not directly visible to the user. This may be used by the system to prioritize operations such as fragment lifecycle updates or loader ordering behavior.

Call startActivity(Intent) on the fragment's containing Activity.

Call startActivity(Intent, Bundle) on the fragment's containing Activity.

Call startActivityForResult(Intent, int) on the fragment's containing Activity.

Call startActivityForResult(Intent, int, Bundle) on the fragment's containing Activity.

Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression:

   getClass().getName() + '@' + Integer.toHexString(hashCode())

See Writing a useful toString method if you intend implementing your own toString method.

Prevents a context menu to be shown for the given view. This method will remove the View.OnCreateContextMenuListener on the view.