Fragment的理解

1.生命周期

  

启动Fragment时：

onAttach
onCreate
onCreateView
onViewCreated
onActivityCreated
onStart
onResume

启动后点击home键：

onPause
onSaveInstanceState
onStop

从home键再次进入:

onStart
onResume

Fragment1-->Fragment2:

fragment1: onPause onStop onDestroyView

fragment2: 

 onAttach
 onCreate
 onCreateView
 onViewCreated
 onActivityCreated
 onStart
 onResume

在回退Fragment2-->Fragment1:


fragment1：onCreateView onActivityCreated onStart onResume

点击back键退出：

onPause
onStop
onDestroyView
onDestroy
onDetach

如果启动2个Fragment后，点击back退出：

两个Fragment交替调用 onPause,onStop。然后一一调用onDestoryView，onDestory,onDetach.

2.Fragent底部导航的使用<忘了看的谁的博客源码了……>

   <1>结构图：

<2> A-E fragment

public class Tab_AFragment extends Fragment {

    private static final String TAG = "Tab_AFragment";
    public Tab_AFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        Log.d(TAG, "onCreateView");
        return inflater.inflate(R.layout.fragment_tab, container, false);
    }

}

 Main.xml 布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#ffffff"
    tools:context="myapplication.com.myfragment.MainActivity">

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:orientation="vertical"
        >

        <FrameLayout
            android:id="@+id/tab_content"
            android:layout_width="fill_parent"
            android:layout_height="0dp"
            android:layout_weight="1.0"
            android:background="#77557799"
            />

        <RadioGroup
            android:id="@+id/tabs_rg"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:gravity="center"

            >
            <RadioButton
                android:id="@+id/tab_rb_a"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:drawableTop="@drawable/tablatestalert"
                android:button="@null"
                android:text="Tab1"
                android:textColor="#000000"
                android:textSize="13sp"
                android:layout_weight="1.0"
                android:gravity="center"
                android:singleLine="true"
                android:checked="true"
                android:background="@drawable/selector_tab"
                />
            <RadioButton
                android:id="@+id/tab_rb_b"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:drawableTop="@drawable/tabsearch"
                android:button="@null"
                android:text="Tab2"
                android:textColor="#000000"
                android:textSize="13sp"
                android:layout_weight="1.0"
                android:gravity="center"
                android:singleLine="true"
                android:background="@drawable/selector_tab"
                />

            <RadioButton
                android:id="@+id/tab_rb_c"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:drawableTop="@drawable/tabrecommd"
                android:button="@null"
                android:text="Tab3"
                android:textColor="#000000"
                android:textSize="13sp"
                android:layout_weight="1.0"
                android:gravity="center"
                android:singleLine="true"
                android:background="@drawable/selector_tab"
                />

            <RadioButton
                android:id="@+id/tab_rb_d"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:drawableTop="@drawable/tabconfigicon"
                android:button="@null"
                android:text="Tab4"
                android:textColor="#000000"
                android:textSize="13sp"
                android:layout_weight="1.0"
                android:gravity="center"
                android:singleLine="true"
                android:background="@drawable/selector_tab"
                />
            <RadioButton
                android:id="@+id/tab_rb_e"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:drawableTop="@drawable/tababoutus"
                android:button="@null"
                android:text="Tab5"
                android:textColor="#000000"
                android:textSize="13sp"
                android:layout_weight="1.0"
                android:gravity="center"
                android:singleLine="true"
                android:background="@drawable/selector_tab"
                />

        </RadioGroup>
    </LinearLayout>
</LinearLayout>

选择：

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- 默认时的图片 -->
    <item android:drawable="@android:color/transparent" android:state_checked="false"/>
    <!-- 选择时的图片 -->
    <item android:drawable="@color/tab_selected_bg" android:state_checked="true"/>
</selector>

MainActivity

public class MainActivity extends AppCompatActivity {
    private RadioGroup rgs;
    public List<Fragment> fragments = new ArrayList<Fragment>();

    public String hello = "hello ";

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

        fragments.add(new Tab_AFragment());
        fragments.add(new Tab_BFragment());
        fragments.add(new Tab_CFragment());
        fragments.add(new Tab_DFragment());
        fragments.add(new Tab_EFragment());


        rgs = (RadioGroup) findViewById(R.id.tabs_rg);

        FragmentTabAdapter tabAdapter = new FragmentTabAdapter(this, fragments, R.id.tab_content, rgs);
        tabAdapter.setOnRgsExtraCheckedChangedListener(new FragmentTabAdapter.OnRgsExtraCheckedChangedListener(){
            @Override
            public void OnRgsExtraCheckedChanged(RadioGroup radioGroup, int checkedId, int index) {
                System.out.println("Extra---- " + index + " checked!!! ");
            }
        });

    }


}
 FragmentTabAdapter

public class FragmentTabAdapter implements RadioGroup.OnCheckedChangeListener{
    /**
     * tab对应的fragments
     */
    private List<Fragment> fragments;
    /**
     * 单选按钮组，用于切换tab
     */
    private RadioGroup rgs;
    /**
     * fragment 所属的activity
     */
    private FragmentActivity fragmentActivity;
    /**
     * activity 中展示fragment的区域id
     */
    private int fragmentContentId;

    /**
     * 当前tab页面的索引
     */
    private int currentTab;

    /**
     * 用于让调用者在切换tab时候增加新的功能
     */
    private OnRgsExtraCheckedChangedListener onRgsExtraCheckedChangedListener;

    public FragmentTabAdapter(FragmentActivity fragmentActivity, List<Fragment> fragments, int fragmentContentId, RadioGroup rgs) {
        this.fragments = fragments;
        this.rgs = rgs;
        this.fragmentActivity = fragmentActivity;
        this.fragmentContentId = fragmentContentId;

        // 默认显示第一页
        FragmentTransaction ft = fragmentActivity.getSupportFragmentManager().beginTransaction();

        ft.add(fragmentContentId, fragments.get(0));
        ft.commit();

        rgs.setOnCheckedChangeListener(this);


    }

    @Override
    public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {
        for(int i = 0; i < rgs.getChildCount(); i++){
            if(rgs.getChildAt(i).getId() == checkedId){
                Fragment fragment = fragments.get(i);
                FragmentTransaction ft = obtainFragmentTransaction(i);

                getCurrentFragment().onPause(); // 暂停当前tab
//                getCurrentFragment().onStop(); // 暂停当前tab

                if(fragment.isAdded()){
//                    fragment.onStart(); // 启动目标tab的onStart()
                    fragment.onResume(); // 启动目标tab的onResume()
                }else{
                    ft.add(fragmentContentId, fragment);
                }
                showTab(i); // 显示目标tab
                ft.commit();

                // 如果设置了切换tab额外功能功能接口
                if(null != onRgsExtraCheckedChangedListener){
                    onRgsExtraCheckedChangedListener.OnRgsExtraCheckedChanged(radioGroup, checkedId, i);
                }

            }
        }

    }

    /**
     * 切换tab
     * @param idx
     */
    private void showTab(int idx){
        for(int i = 0; i < fragments.size(); i++){
            Fragment fragment = fragments.get(i);
            FragmentTransaction ft = obtainFragmentTransaction(idx);

            if(idx == i){
                ft.show(fragment);
            }else{
                ft.hide(fragment);
            }
            ft.commit();
        }
        currentTab = idx; // 更新目标tab为当前tab
    }

    /**
     * 获取一个带动画的FragmentTransaction
     * @param index
     * @return
     */
    private FragmentTransaction obtainFragmentTransaction(int index){
        FragmentTransaction ft = fragmentActivity.getSupportFragmentManager().beginTransaction();
        // 设置切换动画
        if(index > currentTab){
            ft.setCustomAnimations(R.anim.slide_left_in, R.anim.slide_left_out);
        }else{
            ft.setCustomAnimations(R.anim.slide_right_in, R.anim.slide_right_out);
        }
        return ft;
    }

    public int getCurrentTab() {
        return currentTab;
    }

    public Fragment getCurrentFragment(){
        return fragments.get(currentTab);
    }

    public OnRgsExtraCheckedChangedListener getOnRgsExtraCheckedChangedListener() {
        return onRgsExtraCheckedChangedListener;
    }

    public void setOnRgsExtraCheckedChangedListener(OnRgsExtraCheckedChangedListener onRgsExtraCheckedChangedListener) {
        this.onRgsExtraCheckedChangedListener = onRgsExtraCheckedChangedListener;
    }

    /**
     *  切换tab额外功能功能接口
     */
    static class OnRgsExtraCheckedChangedListener{
        public void OnRgsExtraCheckedChanged(RadioGroup radioGroup, int checkedId, int index){

        }
    }

}

<3>效果图

<4>code:

http://pan.baidu.com/s/1gf3KKSz
View Code
 
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原文地址：https://www.cnblogs.com/galibujianbusana/p/6432784.html