Fragment与Activity通信
Activity向Fragment传递数据:在Activity中创建Bundle数据包，并调用Fragment的setArguments(Bundle bundle)方法即可将Bundle数据包传给Fragment.
Fragment向Activity传递数据或Activity需要在Fragment运行中实时通信:在Fragment中定义一个内部回调接口，再让包含该Fragment的Activity实现该回调接口，这样Fragment即可调用该回调方法将数据传给Activity.
Fragment的管理与Fragment事务(Activity管理Fragment主要依靠FragmentManager)
FragmentManager可以完成如下几方面功能
1.使用findFragmentById(int id)或findFragmentByTag(String tag)方法获取指定Fragment;
2.调用popBackStack()方法将Fragment从后台栈中弹出;
3.调用addOnBackStackChangeListener()注册一个监听器，用于监听后台栈的变化.
public class BookListActivity extends Activity implements
BookListFragment.Callbacks
{
// 定义一个旗标，用于标识该应用是否支持大屏幕
private boolean mTwoPane;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// 指定加载R.layout.activity_book_list对应的界面布局文件
// 但实际上该应用会根据屏幕分辨率家在不同的界面布局文件
/*屏幕适配-->创建values-sw600dp、values-large文件夹，创建refs.xml文件如下
<resources>
<item type="layout" name="activity_book_list">
@layout/activity_book_twopane
</item>
</resources>
*/
setContentView(R.layout.activity_book_list);
// 如果加载的界面布局文件中包含ID为book_detail_container的组件
if (findViewById(R.id.book_detail_container) != null)
{
mTwoPane = true;
((BookListFragment) getFragmentManager()
.findFragmentById(R.id.book_list))
.setActivateOnItemClick(true);
}
}
@Override
public void onItemSelected(Integer id)
{
if (mTwoPane)
{
// 创建Bundle，准备向Fragment传入参数
Bundle arguments = new Bundle();
arguments.putInt(BookDetailFragment.ITEM_ID, id);
// 创建BookDetailFragment对象
BookDetailFragment fragment = new BookDetailFragment();
// 向Fragment传入参数
fragment.setArguments(arguments);
// 使用fragment替换book_detail_container容器当前显示的Fragment
getFragmentManager().beginTransaction()
.replace(R.id.book_detail_container, fragment).commit();
}
else
{
// 创建启动BookDetailActivity的Intent
Intent detailIntent = new Intent(this, BookDetailActivity.class);
// 设置传给BookDetailActivity的参数
detailIntent.putExtra(BookDetailFragment.ITEM_ID, id);
// 启动Activity
startActivity(detailIntent);
}
}
}
activity_book_list.xml
<!-- 直接使用BookListFragment作为界面组件 -->
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
android:name="org.crazyit.app.BookListFragment"
android:id="@+id/book_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"/>
activity_book_twopane.xml
<!-- 定义一个水平排列的LinearLayout，并指定使用中等分隔条 -->
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
android:divider="?android:attr/dividerHorizontal"
android:showDividers="middle">
<!-- 添加一个Fragment -->
<fragment
android:name="org.crazyit.app.BookListFragment"
android:id="@+id/book_list"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1" />
<!-- 添加一个FrameLayout容器 -->
<FrameLayout
android:id="@+id/book_detail_container"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="3" />
</LinearLayout>
public class BookListFragment extends ListFragment
{
private Callbacks mCallbacks;
public interface Callbacks
{
public void onItemSelected(Integer id);
}
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// 为该ListFragment设置Adapter
setListAdapter(new ArrayAdapter<BookContent.Book>(getActivity(),
android.R.layout.simple_list_item_activated_1,
android.R.id.text1, BookContent.ITEMS)); //①
}
// 当该Fragment被添加、显示到Activity时，回调该方法
@Override
public void onAttach(Activity activity)
{
super.onAttach(activity);
// 如果Activity没有实现Callbacks接口，抛出异常
if (!(activity instanceof Callbacks))
{
throw new IllegalStateException(
"BookListFragment所在的Activity必须实现Callbacks接口!");
}
// 把该Activity当成Callbacks对象
mCallbacks = (Callbacks) activity;
}
// 当该Fragment从它所属的Activity中被删除时回调该方法
@Override
public void onDetach()
{
super.onDetach();
// 将mCallbacks赋为null。
mCallbacks = null;
}
// 当用户点击某列表项时回调该方法
@Override
public void onListItemClick(ListView listView
, View view, int position, long id)
{
super.onListItemClick(listView, view, position, id);
mCallbacks.onItemSelected(BookContent.ITEMS.get(position).id);
}
public void setActivateOnItemClick(boolean activateOnItemClick)
{
getListView().setChoiceMode(
activateOnItemClick ? ListView.CHOICE_MODE_SINGLE
: ListView.CHOICE_MODE_NONE);
}
}
public class BookDetailActivity extends Activity
{
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// 指定加载/res/layout目录下的activity_book_detail.xml布局文件
// 该界面布局文件内只定义了一个名为book_detail_container的FrameLayout
setContentView(R.layout.activity_book_detail);
// 将ActionBar上应用图标转换成可点击的按钮
getActionBar().setDisplayHomeAsUpEnabled(true);
if (savedInstanceState == null)
{
// 创建BookDetailFragment对象
BookDetailFragment fragment = new BookDetailFragment();
// 创建Bundle对象，
Bundle arguments = new Bundle();
arguments.putInt(BookDetailFragment.ITEM_ID, getIntent()
.getIntExtra(BookDetailFragment.ITEM_ID, 0));
// 向Fragment传入参数
fragment.setArguments(arguments);
// 将指定fragment添加到book_detail_container容器中
getFragmentManager().beginTransaction()
.add(R.id.book_detail_container, fragment).commit();
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
if (item.getItemId() == android.R.id.home)
{
// 创建启动BookListActivity的Intent
Intent intent = new Intent(this, BookListActivity.class);
// 添加额外的Flag，将Activity栈中处于FirstActivity之上的Activity弹出
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
// 启动intent对应的Activity
startActivity(intent);
return true;
}
return super.onOptionsItemSelected(item);
}
}
public class BookDetailFragment extends Fragment
{
public static final String ITEM_ID = "item_id";
// 保存该Fragment显示的Book对象
BookContent.Book book;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// 如果启动该Fragment时包含了ITEM_ID参数
if (getArguments().containsKey(ITEM_ID))
{
book = BookContent.ITEM_MAP.get(getArguments()
.getInt(ITEM_ID));
}
}
// 重写该方法，该方法返回的View将作为Fragment显示的组件
@Override
public View onCreateView(LayoutInflater inflater
, ViewGroup container, Bundle savedInstanceState)
{
// 加载/res/layout/目录下的fragment_book_detail.xml布局文件
View rootView = inflater.inflate(R.layout.fragment_book_detail,
container, false);
if (book != null)
{
// 让book_title文本框显示book对象的title属性
((TextView) rootView.findViewById(R.id.book_title))
.setText(book.title);
// 让book_desc文本框显示book对象的desc属性
((TextView) rootView.findViewById(R.id.book_desc))
.setText(book.desc);
}
return rootView;
}
}
model层
public class BookContent
{
public static class Book
{
public Integer id;
public String title;
public String desc;
public Book(Integer id, String title, String desc)
{
this.id = id;
this.title = title;
this.desc = desc;
}
@Override
public String toString()
{
return title;
}
}
public static List<Book> ITEMS = new ArrayList<Book>();
public static Map<Integer, Book> ITEM_MAP
= new HashMap<Integer, Book>();
static
{
addItem(new Book(1, "疯狂Java讲义"
, "一本全面、深入的Java学习图书，已被多家高校选做教材。"));
addItem(new Book(2, "疯狂Android讲义"
, "Android学习者的首选图书，常年占据京东、当当、亚马逊3大网站Android销量排行榜的榜首"));
addItem(new Book(3, "轻量级Java EE企业应用实战"
, "全面介绍Java EE开发的Struts 2、Spring 3、Hibernate 4框架"));
}
private static void addItem(Book book)
{
ITEMS.add(book);
ITEM_MAP.put(book.id, book);
}
}
