简介
1. Fragments and UI Modularization
2. Fragments and UI Flexibility
- Fragment实现动态布局
- Fragment间交互
3. 生命周期
4. FragmentTransaction
5. Rich Navigation
6. Fragement的交互
Reference

简介

Fragment可以当成Activity的一个界面的一个组成部分，Activity的界面可以完全有不同的Fragment组成

Fragment拥有自己的生命周期和接收、处理用户的事件。可以动态的添加、替换和移除某个Fragment。

1. Fragments and UI Modularization

Fragments实现UI 模块化布局

activity_main.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">
    <!-- List of Book Titles -->
    <fragment
        android:id="@+id/fragmentTitles"
        android:name="com.open.dynamicfragments.BookListFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

    <!-- Description of selected book -->
    <fragment
        android:id="@+id/fragmentDescription"
        android:name="com.open.dynamicfragments.BookDescFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />
</LinearLayout>

fragment_book_desc.xml

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/scrollDescription"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="fill_horizontal"
        android:text="@string/dynamicUiDescription" />
</ScrollView>

fragment_book_list.xml

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/scrollTitles"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <RadioGroup
        android:id="@+id/bookSelectGroup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">

        <RadioButton
            android:id="@+id/dynamicUiBook"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:checked="true"
            android:text="@string/dynamicUiTitle" />

        <RadioButton
            android:id="@+id/android4NewBook"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/android4NewTitle" />
        <!-- Other RadioButtons elided for clarify -->
    </RadioGroup>
</ScrollView>

完整Code

2. Fragments and UI Flexibility

Fragment实现动态布局

功能需求

横屏选择书单，右侧内容变化
竖屏选择书单，开启另外一个Activity

实现逻辑：

横屏main layout包含两个Fragment（BookDescFragment，BookListFragment）在MainActivity中
竖屏main layout一个Fragment（BookListFragment）在MainActivity中；BookDescFragment在另外一个BookDescActivity
判断逻辑：如果BookDescFragment存在main layout中，则更新右侧内容，否则叫起另一个Activity

values-land家中使用refs.xml layout alias方式实现

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <item name="activity_main" type="layout">
        @layout/activity_main_wide
    </item>
</resources>

Fragment间交互

BookListFragment定义Listener
MainActivity中监听，然后调用BookDescFragment中的方法。

完整Code

3. 生命周期

Activity 生命周期

Fragment 生命周期

4. FragmentTransaction

FragmentTransaction 实现Activity中Fragment的灵活管理和切换。

Demo是在Demo 3的基础上进行优化，竖屏改为一个Activity，动态改变现实不同Fragment（bookList和bookDescription)

activity_mian.xml变化：移除fragmentDescription，后续动态替换

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layoutRoot"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <!-- List of Book Titles ** using the ListFragment **-->
    <fragment
        android:id="@+id/fragmentTitles"
        android:name="com.open.dynamicfragments.BookListFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

</LinearLayout>

MainActivity变化：onCreate加入判断，是否动态支援显示；onSelectedBookChanged 动态替换Fragment

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

    FragmentManager fm = getSupportFragmentManager();
    Fragment bookDescFragment =
            fm.findFragmentById(R.id.fragmentDescription);
    // If not found than we're doing dynamic mgmt
    mIsDynamic = bookDescFragment == null || !bookDescFragment.isInLayout();

    // Load the list fragment if necessary
    if (mIsDynamic) {
        // Begin transaction
        FragmentTransaction ft = fm.beginTransaction();
        // Create the Fragment and add
        BookListFragment listFragment = new BookListFragment();
        ft.add(R.id.layoutRoot, listFragment, "bookList");
        ft.commit();
    }
}


 @Override
public void onSelectedBookChanged(int bookIndex) {
    BookDescFragment bookDescFragment;
    FragmentManager fm = getSupportFragmentManager();

    // Check validity of fragment reference
    if (mIsDynamic) {
        // Handle dynamic switch to description fragment
        FragmentTransaction ft = fm.beginTransaction();
        bookDescFragment = new BookDescFragment();

        // Create the fragment and attach book index
        bookDescFragment = new BookDescFragment();
        Bundle args = new Bundle();
        args.putInt(BookDescFragment.BOOK_INDEX, bookIndex);
        bookDescFragment.setArguments(args);

        // Replace the book list with the description
        ft.replace(R.id.layoutRoot,
                bookDescFragment, "bookDescription");
        ft.addToBackStack(null);

        //ft.setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out);
        ft.commit();
    } else {
        // Use the already visible description fragment
        bookDescFragment = (BookDescFragment)
                fm.findFragmentById(R.id.fragmentDescription);
        bookDescFragment.setBook(bookIndex);
    }
}

BookDescFragment变化： onCreateView加入getArguments处理

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View viewHierarchy = inflater.inflate(R.layout.fragment_book_desc, container, false);

    initView(viewHierarchy);

    return viewHierarchy;
}

private void initView(View viewHierarchy) {
    // Load array of book descriptions
    mBookDescriptions = getResources().getStringArray(R.array.bookDescriptions);
    // Get reference to book description text view
    mBookDescriptionTextView = (TextView)
            viewHierarchy.findViewById(R.id.bookDescription);

    // Retrieve the book index if attached
    Bundle args = getArguments();
    int bookIndex = args != null ?
            args.getInt(BOOK_INDEX, BOOK_INDEX_NOT_SET) :
            BOOK_INDEX_NOT_SET;

    // If we find the book index, use it
    if (bookIndex != BOOK_INDEX_NOT_SET) {
        setBook(bookIndex);
    }
}

Swipe navigation and Action Bar navigation, you could check android default template here:

6. Fragement的交互

Fragment可以通过getActivity获取FragmentActivity的实例，也可以通过findFragmentById的方式获取Fragment。

因此Fragment之间的交互有很多种：

1) Fragment之间通过Activity通讯
- 使用方法：Fragment可以通过getActivity
- 缺点：Fragment要持有Activity的实例
- 优点：避开了多个Fragment之间的耦合
2）Fragment之间直接通讯
- 使用方法：findFragmentById的方式获取Fragment
- 缺点：多个Fragment直接耦合
- 优点：不通过Activity传递
3）使用EventBus解耦
- 使用方法：参照EventBus使用方法
- 优点：实现Activity，Fragment直接解耦，可定制线程环境
- 缺点：需要增加EventBus类，逻辑复杂时可能出现nested Event
4) RxJava
- 使用方法：放弃RxBus，拥抱RxJava，透出Observe对象
- 优点：不通过第三方传递，直接投给目标，可定制线程环境，面向响应式编程
- 缺点：Fragment之间耦合
5）LocalBroadcast方式
- 使用方法：参考LocalBroadcast源码解析和使用
- 优点：解除耦合，较EventBus性能差不太多
- 缺点：代码量多，依赖Context注入，运行在主线程，若有耗时操作可能会影响UX

EventBus和LocalBroadcast的比较

Reference

Creating Dynamic UI with Android Fragments

Android 基础：Fragment，看这篇就够了（上）

Activity与Fragment的生命周期

目录

简介