The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...
/*
* Copyright (C) 2011 The Android开源工程
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.hcgallery;
import android.app.ActionBar;
import android.app.Activity;
import android.app.FragmentTransaction;
import android.app.ListFragment;
import android.content.ClipData;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.View;
import android.view.ViewTreeObserver;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemLongClickListener;
import android.widget.ArrayAdapter;
import android.widget.FrameLayout;
import android.widget.FrameLayout.LayoutParams;
import android.widget.ListView;
import android.widget.TextView;
/**
* Fragment that shows the list of images
* As an extension of ListFragment, this fragment uses a default layout
* that includes a single ListView, which you can acquire with getListView()
* When running on a screen size smaller than "large", this fragment appears alone
* in MainActivity. In this case, selecting a list item opens the ContentActivity,
* which likewise holds only the ContentFragment.
*/
public class TitlesFragment extends ListFragment implements ActionBar.TabListener {
OnItemSelectedListener mListener;
private int mCategory = 0;
private int mCurPosition = 0;
private boolean mDualFragments = false;
/** Container Activity must implement this interface and we ensure
* that it does during the onAttach() callback
*/
public interface OnItemSelectedListener {
public void onItemSelected(int category, int position);
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// Check that the container activity has implemented the callback interface
try {
mListener = (OnItemSelectedListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnItemSelectedListener");
}
}
/** This is where we perform setup for the fragment that's either
* not related to the fragment's layout or must be done after the layout is drawn.
* Notice that this fragment does not implement onCreateView(), because it extends
* ListFragment, which includes a ListView as the root view by default, so there's
* no need to set up the layout.
*/
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
ContentFragment frag = (ContentFragment) getFragmentManager()
.findFragmentById(R.id.content_frag);
if (frag != null) mDualFragments = true;
ActionBar bar = getActivity().getActionBar();
bar.setDisplayHomeAsUpEnabled(false);
bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Must call in order to get callback to onCreateOptionsMenu()
setHasOptionsMenu(true);
Directory.initializeDirectory();
for (int i = 0; i < Directory.getCategoryCount(); i++) {
bar.addTab(bar.newTab().setText(Directory.getCategory(i).getName())
.setTabListener(this));
}
//Current position should survive screen rotations.
if (savedInstanceState != null) {
mCategory = savedInstanceState.getInt("category");
mCurPosition = savedInstanceState.getInt("listPosition");
bar.selectTab(bar.getTabAt(mCategory));
}
populateTitles(mCategory);
ListView lv = getListView();
lv.setCacheColorHint(Color.TRANSPARENT); // Improves scrolling performance
if (mDualFragments) {
// Highlight the currently selected item
lv.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
// Enable drag and dropping
lv.setOnItemLongClickListener(new OnItemLongClickListener() {
public boolean onItemLongClick(AdapterView<?> av, View v, int pos, long id) {
final String title = (String) ((TextView) v).getText();
// Set up clip data with the category||entry_id format.
final String textData = String.format("%d||%d", mCategory, pos);
ClipData data = ClipData.newPlainText(title, textData);
v.startDrag(data, new MyDragShadowBuilder(v), null, 0);
return true;
}
});
}
// If showing both fragments, select the appropriate list item by default
if (mDualFragments) selectPosition(mCurPosition);
// Attach a GlobalLayoutListener so that we get a callback when the layout
// has finished drawing. This is necessary so that we can apply top-margin
// to the ListView in order to dodge the ActionBar. Ordinarily, that's not
// necessary, but we've set the ActionBar to "overlay" mode using our theme,
// so the layout does not account for the action bar position on its own.
ViewTreeObserver observer = getListView().getViewTreeObserver();
observer.addOnGlobalLayoutListener(layoutListener);
}
@Override
public void onDestroyView() {
super.onDestroyView();
// Always detach ViewTreeObserver listeners when the view tears down
getListView().getViewTreeObserver().removeGlobalOnLayoutListener(layoutListener);
}
/** Attaches an adapter to the fragment's ListView to populate it with items */
public void populateTitles(int category) {
DirectoryCategory cat = Directory.getCategory(category);
String[] items = new String[cat.getEntryCount()];
for (int i = 0; i < cat.getEntryCount(); i++)
items[i] = cat.getEntry(i).getName();
// Convenience method to attach an adapter to ListFragment's ListView
setListAdapter(new ArrayAdapter<String>(getActivity(),
R.layout.title_list_item, items));
mCategory = category;
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
// Send the event to the host activity via OnItemSelectedListener callback
mListener.onItemSelected(mCategory, position);
mCurPosition = position;
}
/** Called to select an item from the listview */
public void selectPosition(int position) {
// Only if we're showing both fragments should the item be "highlighted"
if (mDualFragments) {
ListView lv = getListView();
lv.setItemChecked(position, true);
}
// Calls the parent activity's implementation of the OnItemSelectedListener
// so the activity can pass the event to the sibling fragment as appropriate
mListener.onItemSelected(mCategory, position);
}
@Override
public void onSaveInstanceState (Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("listPosition", mCurPosition);
outState.putInt("category", mCategory);
}
/** This defines how the draggable list items appear during a drag event */
private class MyDragShadowBuilder extends View.DragShadowBuilder {
private Drawable mShadow;
public MyDragShadowBuilder(View v) {
super(v);
final TypedArray a = v.getContext().obtainStyledAttributes(R.styleable.AppTheme);
mShadow = a.getDrawable(R.styleable.AppTheme_listDragShadowBackground);
mShadow.setCallback(v);
mShadow.setBounds(0, 0, v.getWidth(), v.getHeight());
a.recycle();
}
@Override
public void onDrawShadow(Canvas canvas) {
super.onDrawShadow(canvas);
mShadow.draw(canvas);
getView().draw(canvas);
}
}
// Because the fragment doesn't have a reliable callback to notify us when
// the activity's layout is completely drawn, this OnGlobalLayoutListener provides
// the necessary callback so we can add top-margin to the ListView in order to dodge
// the ActionBar. Which is necessary because the ActionBar is in overlay mode, meaning
// that it will ordinarily sit on top of the activity layout as a top layer and
// the ActionBar height can vary. Specifically, when on a small/normal size screen,
// the action bar tabs appear in a second row, making the action bar twice as tall.
ViewTreeObserver.OnGlobalLayoutListener layoutListener = new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
int barHeight = getActivity().getActionBar().getHeight();
ListView listView = getListView();
FrameLayout.LayoutParams params = (LayoutParams) listView.getLayoutParams();
// The list view top-margin should always match the action bar height
if (params.topMargin != barHeight) {
params.topMargin = barHeight;
listView.setLayoutParams(params);
}
// The action bar doesn't update its height when hidden, so make top-margin zero
if (!getActivity().getActionBar().isShowing()) {
params.topMargin = 0;
listView.setLayoutParams(params);
}
}
};
/* The following are callbacks implemented for the ActionBar.TabListener,
* which this fragment implements to handle events when tabs are selected.
*/
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
TitlesFragment titleFrag = (TitlesFragment) getFragmentManager()
.findFragmentById(R.id.titles_frag);
titleFrag.populateTitles(tab.getPosition());
if (mDualFragments) {
titleFrag.selectPosition(0);
}
}
/* These must be implemented, but we don't use them */
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
}