# FragmentMenu

**Repository Path**: amqr/FragmentMenu

## Basic Information

- **Project Name**: FragmentMenu
- **Description**: 记录Fragment声明周期，避免重复创建，每个Fragment独立拥有Toobar和menu
- **Primary Language**: Java
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 1
- **Forks**: 0
- **Created**: 2016-11-26
- **Last Updated**: 2020-12-19

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

>Toorbar现在已经被广泛使用了，但是多个Fragment之间使用Toorbar的使用可能会遇到menu消失的问题，单就本来这点不必成文，但是一想到好像还没有写过关Fragment声明周期的和复用的文章，就干脆记录一下算了，后面如果需要拿起来参考也算可以。


文章分三点进行描述，第一点说的是Fragment的生命周期，大可忽略之，第二点说的是如何利用add和hide避免重复创建Fragment，老生常谈也可忽略之，第三点说是让每一个Toolbar对应不同的Toolbar的menu，这个还是可以稍微参考一下的。

# 一、以事务replace方式简述生命周期


先上图，再代码，后分析

![gif依次12341.gif](http://upload-images.jianshu.io/upload_images/1083096-b168782195ee38e8.gif?imageMogr2/auto-orient/strip)


上代码

Activity
```
public class StyleFirstActivity extends AppCompatActivity implements RadioGroup.OnCheckedChangeListener {
    private RadioGroup mRbTab;
    private RadioButton mRbOne;
    private RadioButton mRbTwo;
    private RadioButton mRbThree;
    private RadioButton mRbFour;
    private OneFragment oneFragment;
    private TwoFragment twoFragment;
    private ThreeFragment threeFragment;
    private FourFragment fourFragment;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mRbTab = (RadioGroup) findViewById(R.id.mRbTab);
        mRbOne = (RadioButton) findViewById(R.id.mRbOne);
        mRbTwo = (RadioButton) findViewById(R.id.mRbTwo);
        mRbThree = (RadioButton) findViewById(R.id.mRbThree);
        mRbFour = (RadioButton) findViewById(R.id.mRbFour);
        mRbTab.setOnCheckedChangeListener(this);
        commitOneFrag();
    }
    // MainActivty实现接口的必须复写的方法
    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        FragmentManager fm = getSupportFragmentManager(); // getSupportFragmentManager(); 才是v4的
        FragmentTransaction transaction = fm.beginTransaction();  // Fragment的事务
        switch (checkedId) {
            case R.id.mRbOne:
                if (oneFragment == null) {
                    oneFragment = new OneFragment();
                }
                transaction.replace(R.id.mFlWaitReplace, oneFragment);
                break;
            case R.id.mRbTwo:
                if (twoFragment == null) {
                    twoFragment = new TwoFragment();
                }
                transaction.replace(R.id.mFlWaitReplace, twoFragment);
                break;
            case R.id.mRbThree:
                if (threeFragment == null) {
                    threeFragment = new ThreeFragment();
                }
                transaction.replace(R.id.mFlWaitReplace, threeFragment);
                break;
            case R.id.mRbFour:
                if (fourFragment == null) {
                    fourFragment = new FourFragment();
                }
                transaction.replace(R.id.mFlWaitReplace, fourFragment);
                break;
        }
        transaction.commit();
    }
    private void commitOneFrag() {
        OneFragment oneFrag = new OneFragment();
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.mFlWaitReplace, oneFrag);
        ft.commit();
    }
}
```


布局文件
```
<?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:layout_width="match_parent"
              android:layout_height="match_parent"
              android:background="#fff2f2f2"
              tools:context=".activity.StyleFirstActivity"
              android:orientation="vertical"
    >
    <FrameLayout
        android:id="@+id/mFlWaitReplace"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        ></FrameLayout>
    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="#ffdddddd"
        />
    <RadioGroup
        android:id="@+id/mRbTab"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:layout_gravity="center_vertical"
        android:orientation="horizontal" >
        <RadioButton
            android:id="@+id/mRbOne"
            style="@style/tab_style"
            android:drawableTop="@drawable/ic1"
            android:text="首页" />
        <RadioButton
            android:id="@+id/mRbTwo"
            style="@style/tab_style"
            android:drawableTop="@drawable/ic2"
            android:text="社区" />
        <RadioButton
            android:id="@+id/mRbThree"
            style="@style/tab_style"
            android:drawableTop="@drawable/ic3"
            android:text="购物车" />
        <RadioButton
            android:id="@+id/mRbFour"
            style="@style/tab_style"
            android:drawableTop="@drawable/ic4"
            android:text="我的" />
    </RadioGroup>
</LinearLayout>
```
.
.
.
Fragment，四个都类似，以为OneFragmemt为例子
```
public class OneFragment extends Fragment {
    private View rootView;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater infater, ViewGroup container, Bundle savedInstanceState) {
        Log.d(GeneralConst.TAG,"OneFragment --- onCreateView");
        rootView = View.inflate(getActivity(), R.layout.fragment_one, null);
        initView();
        return rootView;
    }
    private void initView() {
        rootView.findViewById(R.id.mTvOne).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(getActivity(),"FragmentOne的Tv点击",Toast.LENGTH_SHORT).show();
            }
        });
    }
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        Log.d(GeneralConst.TAG,"OneFragment --- onAttach");
    }
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(GeneralConst.TAG,"OneFragment --- onCreate");
    }
    @Override
    public void onStart() {
        super.onStart();
        Log.d(GeneralConst.TAG,"OneFragment --- onStart");
    }
    @Override
    public void onResume() {
        super.onResume();
        Log.d(GeneralConst.TAG,"OneFragment --- onResume");
    }
    @Override
    public void onPause() {
        super.onPause();
        Log.d(GeneralConst.TAG,"OneFragment --- onPause");
    }
    @Override
    public void onStop() {
        super.onStop();
        Log.d(GeneralConst.TAG,"OneFragment --- onStop");
    }
    @Override
    public void onDestroyView() {
        super.onDestroyView();
        Log.d(GeneralConst.TAG,"OneFragment --- onDestroyView");
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d(GeneralConst.TAG,"OneFragment --- onDestroy");
    }
    @Override
    public void onDetach() {
        super.onDetach();
        Log.d(GeneralConst.TAG,"OneFragment --- onDetach");
    }
}
```



Fragment和Activity的生命周期较为相似了。
只是Fragment有几个Activity中没有的新方法，这里需要重点介绍一下：

* onAttach方法：Fragment和Activity建立关联的时候调用。
* onCreateView方法：为Fragment加载布局时调用。
* onActivityCreated方法：当Activity中的onCreate方法执行完后调用。
* onDestroyView方法：Fragment中的布局被移除时调用。
* onDetach方法：Fragment和Activity解除关联的时候调用。

进入该Activity，依次点击第一，第二，第三，第四，第一个Fragment


现在对点击进行分析：

执行了5个生命周期方法，对比其他的这里只是，这里这是执行了5个，原因是因为我们一进入这个Activity默认就进入了第一个Activity，然后我们再次点击了第一个，相当于重复点击了两次第一个。

```
11-23 08:30:28.712 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onAttach

11-23 08:30:28.712 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onCreate

11-23 08:30:28.712 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onCreateView

11-23 08:30:28.712 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onStart

11-23 08:30:28.712 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onResume

--- 分割线 ---

11-23 08:30:31.269 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onAttach

11-23 08:30:31.269 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onCreate

11-23 08:30:31.269 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onPause

11-23 08:30:31.269 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onStop

11-23 08:30:31.269 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onDestroyView

11-23 08:30:31.269 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onDestroy

11-23 08:30:31.269 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onDetach

11-23 08:30:31.269 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onCreateView

11-23 08:30:31.270 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onStart

11-23 08:30:31.270 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onResume

--- 分割线 ---

11-23 08:30:32.350 11279-11279/com.amqr.testfragment D/FragTest: TwoFragment --- onAttach

11-23 08:30:32.350 11279-11279/com.amqr.testfragment D/FragTest: TwoFragment --- onCreate

11-23 08:30:32.350 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onPause

11-23 08:30:32.350 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onStop

11-23 08:30:32.350 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onDestroyView

11-23 08:30:32.350 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onDestroy

11-23 08:30:32.350 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onDetach

11-23 08:30:32.350 11279-11279/com.amqr.testfragment D/FragTest: TwoFragment --- onCreateView

11-23 08:30:32.351 11279-11279/com.amqr.testfragment D/FragTest: TwoFragment --- onStart

11-23 08:30:32.351 11279-11279/com.amqr.testfragment D/FragTest: TwoFragment --- onResume

--- 分割线 ---

11-23 08:30:33.033 11279-11279/com.amqr.testfragment D/FragTest: ThreeFragment --- onAttach

11-23 08:30:33.033 11279-11279/com.amqr.testfragment D/FragTest: ThreeFragment --- onCreate

11-23 08:30:33.033 11279-11279/com.amqr.testfragment D/FragTest: TwoFragment --- onPause

11-23 08:30:33.033 11279-11279/com.amqr.testfragment D/FragTest: TwoFragment --- onStop

11-23 08:30:33.033 11279-11279/com.amqr.testfragment D/FragTest: TwoFragment --- onDestroyView

11-23 08:30:33.033 11279-11279/com.amqr.testfragment D/FragTest: TwoFragment --- onDestroy

11-23 08:30:33.033 11279-11279/com.amqr.testfragment D/FragTest: TwoFragment --- onDetach

11-23 08:30:33.033 11279-11279/com.amqr.testfragment D/FragTest: ThreeFragment --- onCreateView

11-23 08:30:33.035 11279-11279/com.amqr.testfragment D/FragTest: ThreeFragment --- onStart

11-23 08:30:33.035 11279-11279/com.amqr.testfragment D/FragTest: ThreeFragment --- onResume

--- 分割线 ---

11-23 08:30:33.699 11279-11279/com.amqr.testfragment D/FragTest: FourFragment --- onAttach

11-23 08:30:33.700 11279-11279/com.amqr.testfragment D/FragTest: FourFragment --- onCreate

11-23 08:30:33.700 11279-11279/com.amqr.testfragment D/FragTest: ThreeFragment --- onPause

11-23 08:30:33.700 11279-11279/com.amqr.testfragment D/FragTest: ThreeFragment --- onStop

11-23 08:30:33.700 11279-11279/com.amqr.testfragment D/FragTest: ThreeFragment --- onDestroyView

11-23 08:30:33.700 11279-11279/com.amqr.testfragment D/FragTest: ThreeFragment --- onDestroy

11-23 08:30:33.700 11279-11279/com.amqr.testfragment D/FragTest: ThreeFragment --- onDetach

11-23 08:30:33.700 11279-11279/com.amqr.testfragment D/FragTest: FourFragment --- onCreateView

11-23 08:30:33.700 11279-11279/com.amqr.testfragment D/FragTest: FourFragment --- onStart

11-23 08:30:33.700 11279-11279/com.amqr.testfragment D/FragTest: FourFragment --- onResume

--- 分割线 ---

11-23 08:30:34.833 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onAttach

11-23 08:30:34.833 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onCreate

11-23 08:30:34.833 11279-11279/com.amqr.testfragment D/FragTest: FourFragment --- onPause

11-23 08:30:34.833 11279-11279/com.amqr.testfragment D/FragTest: FourFragment --- onStop

11-23 08:30:34.833 11279-11279/com.amqr.testfragment D/FragTest: FourFragment --- onDestroyView

11-23 08:30:34.833 11279-11279/com.amqr.testfragment D/FragTest: FourFragment --- onDestroy

11-23 08:30:34.834 11279-11279/com.amqr.testfragment D/FragTest: FourFragment --- onDetach

11-23 08:30:34.834 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onCreateView

11-23 08:30:34.839 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onStart

11-23 08:30:34.839 11279-11279/com.amqr.testfragment D/FragTest: OneFragment --- onResume

```

如上，我们看的出来，以这种方式构建，每次点击切换到一个Fragment，至少都会执行5个方法

```
onAttach

onCreate

 onCreateView

onStart

onResume
```

如果是切换那么会相应交织着上一个被销毁的过程（正因为上一个被销毁，所以我们点击新的Fragment才会有重新创建）

这里关键是明白一点，我们这里的新切换的Fragment都会有一个onCreate和onCreateView过程，这在大多数情况下不是我们想要的，对于页面复杂的Fragment是比较消耗内存的，这不是我们想看到的。

产生这个问题的主要原因是我们采用了replace()方法来替换Fragment。

关于这个老生常谈的问题就到此为止。

> 关于Fragment生命周期可以参考[Android Fragment完全解析，关于碎片你所需知道的一切](http://blog.csdn.net/sinyu890807/article/details/8881711)


# 二、利用事务的add和hide复用Fragment

一样，一图二码三分析

![复用12341332.gif](http://upload-images.jianshu.io/upload_images/1083096-8db059534feec221.gif?imageMogr2/auto-orient/strip)

Activity
```
public class StyleSecondActivity extends AppCompatActivity{
    private Button[] mTabs;
    // ======== 四个TAB
    private OneFragment sOneFragment;
    private TwoFragment sTwoFragment;
    private ThreeFragment sThreeFragment;
    private FourFragment sFourFragment;
    private Fragment[] fragments;
    private int index;
    private int currentTabIndex;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_style_second);
        mTabs = new Button[4];
        mTabs[0] = (Button) findViewById(R.id.mBtOneFragment);
        mTabs[1] = (Button) findViewById(R.id.mBtTwoFragment);
        mTabs[2] = (Button) findViewById(R.id.mBtThreeFragment);
        mTabs[3] = (Button) findViewById(R.id.mBtFourFragment);
        // select first tab
        mTabs[0].setSelected(true);
        // 实例化Tab
        sOneFragment = new OneFragment();
        sTwoFragment = new TwoFragment();
        sThreeFragment = new ThreeFragment();
        sFourFragment = new FourFragment();
        fragments = new Fragment[]{sOneFragment, sTwoFragment,  sThreeFragment, sFourFragment};
        // 一开始只把 第一个 和 第二个 Fragment添加到事务里面,(方便切换时有数据)
        // 然后默认展示第一个,第二个隐藏起来
        getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, sOneFragment)
                .add(R.id.fragment_container, sTwoFragment).hide(sTwoFragment).show(sOneFragment)
                .commit();
    }
    /**
     * 每一个按钮都带有android:onClick="onTabClicked"
     * 不采用常规的复写onClick而采用这种方式,是为了统一操作这些按钮
     * @param view
     */
    public void onTabClicked(View view) {
        switch (view.getId()) {
            case R.id.mBtOneFragment:
                index = 0;
                break;
            case R.id.mBtTwoFragment:
                index = 1;
                break;
            case R.id.mBtThreeFragment:
                index = 2;
                break;
            case R.id.mBtFourFragment:
                index = 3;
                break;
        }
        if (currentTabIndex != index) { // 切换了Fragment
            FragmentTransaction trx = getSupportFragmentManager().beginTransaction();
            trx.hide(fragments[currentTabIndex]); // 隐藏原来的
            if (!fragments[index].isAdded()) { // 如果当前的没有被添加到FragmentTransaction,添加之
                trx.add(R.id.fragment_container, fragments[index]);
            }
            trx.show(fragments[index]).commit(); // 添加事务,切换Fragment
        }
        mTabs[currentTabIndex].setSelected(false);
        mTabs[index].setSelected(true);
        currentTabIndex = index;
    }
}
```


布局文件
```
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:id="@+id/mainLayout"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                 >
    <LinearLayout
        android:id="@+id/main_bottom"
        android:layout_width="match_parent"
        android:layout_height="52dp"
        android:layout_alignParentBottom="true"
        android:background="@color/gray1"
        android:gravity="center_vertical"
        android:orientation="horizontal" >
        <RelativeLayout
            android:id="@+id/btn_container_conversation"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1" >
            <Button
                android:id="@+id/mBtOneFragment"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="@color/transparent"
                android:drawableTop="@drawable/ic1"
                android:onClick="onTabClicked"
                android:paddingBottom="2dip"
                android:paddingTop="7dip"
                android:scaleType="matrix"
                android:text="诗词"
                android:textColor="@color/em_main_botton_text_color"
                android:textSize="10sp" />
        </RelativeLayout>
        <RelativeLayout
            android:id="@+id/btn_container_address_list"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1" >
            <Button
                android:id="@+id/mBtTwoFragment"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="@color/transparent"
                android:drawableTop="@drawable/ic2"
                android:onClick="onTabClicked"
                android:paddingBottom="2dip"
                android:paddingTop="7dip"
                android:scaleType="matrix"
                android:text="歌赋"
                android:textColor="@color/em_main_botton_text_color"
                android:textSize="10sp" />
、
        </RelativeLayout>
        <RelativeLayout
            android:id="@+id/btn_info"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1" >
            <Button
                android:id="@+id/mBtThreeFragment"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="@color/gray1"
                android:drawableTop="@drawable/ic3"
                android:onClick="onTabClicked"
                android:paddingBottom="2dip"
                android:paddingTop="7dip"
                android:scaleType="matrix"
                android:text="春秋"
                android:textColor="@color/em_main_botton_text_color"
                android:textSize="10sp" />
        </RelativeLayout>
        <RelativeLayout
            android:id="@+id/btn_container_me"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1" >
            <Button
                android:id="@+id/mBtFourFragment"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="@color/transparent"
                android:drawableTop="@drawable/ic4"
                android:onClick="onTabClicked"
                android:paddingBottom="2dip"
                android:paddingTop="7dip"
                android:scaleType="matrix"
                android:text="大学"
                android:textColor="@color/em_main_botton_text_color"
                android:textSize="10sp" />
        </RelativeLayout>
    </LinearLayout>
    <RelativeLayout
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@id/main_bottom" />
</RelativeLayout>
```
这里的布局我调整了一下，这样的布局使用了后期需要添加比如小红点之类的特殊需求

至于Fragment，同第一大点，就不附加了。


.
.
.

分析

运行，然会我们分别点击  1234 1332 ，（1代表第一个Fragment）

```
11-23 09:45:28.081 16526-16526/com.amqr.testfragment D/FragTest: OneFragment --- onAttach
11-23 09:45:28.082 16526-16526/com.amqr.testfragment D/FragTest: OneFragment --- onCreate
11-23 09:45:28.082 16526-16526/com.amqr.testfragment D/FragTest: TwoFragment --- onAttach
11-23 09:45:28.082 16526-16526/com.amqr.testfragment D/FragTest: TwoFragment --- onCreate
11-23 09:45:28.082 16526-16526/com.amqr.testfragment D/FragTest: OneFragment --- onCreateView
11-23 09:45:28.082 16526-16526/com.amqr.testfragment D/FragTest: TwoFragment --- onCreateView
11-23 09:45:28.083 16526-16526/com.amqr.testfragment D/FragTest: OneFragment --- onStart
11-23 09:45:28.083 16526-16526/com.amqr.testfragment D/FragTest: TwoFragment --- onStart
11-23 09:45:28.083 16526-16526/com.amqr.testfragment D/FragTest: OneFragment --- onResume
11-23 09:45:28.083 16526-16526/com.amqr.testfragment D/FragTest: TwoFragment --- onResume
--- 分割线 ---
11-23 09:45:32.124 16526-16526/com.amqr.testfragment D/FragTest: ThreeFragment --- onAttach
11-23 09:45:32.124 16526-16526/com.amqr.testfragment D/FragTest: ThreeFragment --- onCreate
11-23 09:45:32.124 16526-16526/com.amqr.testfragment D/FragTest: ThreeFragment --- onCreateView
11-23 09:45:32.125 16526-16526/com.amqr.testfragment D/FragTest: ThreeFragment --- onStart
11-23 09:45:32.125 16526-16526/com.amqr.testfragment D/FragTest: ThreeFragment --- onResume

--- 分割线 ---

11-23 09:45:33.003 16526-16526/com.amqr.testfragment D/FragTest: FourFragment --- onAttach
11-23 09:45:33.003 16526-16526/com.amqr.testfragment D/FragTest: FourFragment --- onCreate
11-23 09:45:33.004 16526-16526/com.amqr.testfragment D/FragTest: FourFragment --- onCreateView
11-23 09:45:33.004 16526-16526/com.amqr.testfragment D/FragTest: FourFragment --- onStart
11-23 09:45:33.004 16526-16526/com.amqr.testfragment D/FragTest: FourFragment --- onResume
```

我们一旦进入Activity，首先因为代码的关系，我们先让Fragment的事务添加进入第一个和第二个Fragment

所以在什么都没有点击的情况下，先执行了

```
11-23 09:45:28.081 16526-16526/com.amqr.testfragment D/FragTest: OneFragment --- onAttach
11-23 09:45:28.082 16526-16526/com.amqr.testfragment D/FragTest: OneFragment --- onCreate
11-23 09:45:28.082 16526-16526/com.amqr.testfragment D/FragTest: TwoFragment --- onAttach
11-23 09:45:28.082 16526-16526/com.amqr.testfragment D/FragTest: TwoFragment --- onCreate
11-23 09:45:28.082 16526-16526/com.amqr.testfragment D/FragTest: OneFragment --- onCreateView
11-23 09:45:28.082 16526-16526/com.amqr.testfragment D/FragTest: TwoFragment --- onCreateView
11-23 09:45:28.083 16526-16526/com.amqr.testfragment D/FragTest: OneFragment --- onStart
11-23 09:45:28.083 16526-16526/com.amqr.testfragment D/FragTest: TwoFragment --- onStart
11-23 09:45:28.083 16526-16526/com.amqr.testfragment D/FragTest: OneFragment --- onResume
11-23 09:45:28.083 16526-16526/com.amqr.testfragment D/FragTest: TwoFragment --- onResume
```
然会我们点击分别点击1和2，日志没有变化，这就对了，这就是我们想要的结果

我们点击3的时候，日志输出了
```
11-23 09:45:32.124 16526-16526/com.amqr.testfragment D/FragTest: ThreeFragment --- onAttach
11-23 09:45:32.124 16526-16526/com.amqr.testfragment D/FragTest: ThreeFragment --- onCreate
11-23 09:45:32.124 16526-16526/com.amqr.testfragment D/FragTest: ThreeFragment --- onCreateView
11-23 09:45:32.125 16526-16526/com.amqr.testfragment D/FragTest: ThreeFragment --- onStart
11-23 09:45:32.125 16526-16526/com.amqr.testfragment D/FragTest: ThreeFragment --- onResume
```

我们点击4的时候，日志产生的结果是
```
11-23 09:45:33.003 16526-16526/com.amqr.testfragment D/FragTest: FourFragment --- onAttach

11-23 09:45:33.003 16526-16526/com.amqr.testfragment D/FragTest: FourFragment --- onCreate

11-23 09:45:33.004 16526-16526/com.amqr.testfragment D/FragTest: FourFragment --- onCreateView

11-23 09:45:33.004 16526-16526/com.amqr.testfragment D/FragTest: FourFragment --- onStart

11-23 09:45:33.004 16526-16526/com.amqr.testfragment D/FragTest: FourFragment --- onResume
```

（因为3和4我们之前还没有添加进入事务里面）

再后来，我们分别切换到1、3、3和4的时候，日志无变化，这也对了。

因为我们采取的是add和hide，添加和隐藏嘛。

.
.
.

# 三、每一个Fragment对应一个Toolbar和menu


一图二码三分析


![nemu.gif](http://upload-images.jianshu.io/upload_images/1083096-9c33d87bc4acf8b4.gif?imageMogr2/auto-orient/strip)

gif说明：第二个Fragment弹出菜单的的红色是因为模拟器的关系，真机完美运行你懂得。


上代码
Activity
以这种add和hide的方式就不会每次都执行onCreateView，避免效果必要的内存。
```
/**
 *
 * 整体思路,一进入Activity只add进入头两个Fragment,而且hide第二个,展示第一个
 * 以后如果切换到任意的Fragment,那么先判断事务里面有没有这个Fragment,
 * 无则加之,然后隐藏上一个,展示当前新切换到的
 * 有则隐藏上一个,展示当前的新切换到的
 */
public class StyleSecondActivity extends AppCompatActivity {

    private Button[] mTabs;

    // ======== 四个TAB
    private OneFragment sOneFragment;
    private TwoFragment sTwoFragment;
    private ThreeFragment sThreeFragment;
    private FourFragment sFourFragment;


    private Fragment[] fragments;
    private int index;
    private int currentTabIndex;

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

        mTabs = new Button[4];
        mTabs[0] = (Button) findViewById(R.id.mBtOneFragment);
        mTabs[1] = (Button) findViewById(R.id.mBtTwoFragment);
        mTabs[2] = (Button) findViewById(R.id.mBtThreeFragment);
        mTabs[3] = (Button) findViewById(R.id.mBtFourFragment);



        // select first tab
        mTabs[0].setSelected(true);

        // 实例化Tab
        sOneFragment = new OneFragment();
        sTwoFragment = new TwoFragment();
        sThreeFragment = new ThreeFragment();
        sFourFragment = new FourFragment();

        fragments = new Fragment[]{sOneFragment, sTwoFragment,  sThreeFragment, sFourFragment};

        // 一开始只把 第一个 和 第二个 Fragment添加到事务里面,(方便切换时有数据)
        // 然后默认展示第一个,第二个隐藏起来
        getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, sOneFragment)
                .add(R.id.fragment_container, sTwoFragment).hide(sTwoFragment).show(sOneFragment)
                .commit();
    }

    /**
     * 每一个按钮都带有android:onClick="onTabClicked"
     * 不采用常规的复写onClick而采用这种方式,是为了统一操作这些按钮
     * @param view
     */
    public void onTabClicked(View view) {
        switch (view.getId()) {
            case R.id.mBtOneFragment:
                index = 0;
                break;
            case R.id.mBtTwoFragment:
                index = 1;
                break;

            case R.id.mBtThreeFragment:
                index = 2;
                break;
            case R.id.mBtFourFragment:
                index = 3;
                break;
        }
        if (currentTabIndex != index) { // 切换了Fragment
            FragmentTransaction trx = getSupportFragmentManager().beginTransaction();

            trx.hide(fragments[currentTabIndex]); // 隐藏原来的
            if (!fragments[index].isAdded()) { // 如果当前的没有被添加到FragmentTransaction,添加之
                trx.add(R.id.fragment_container, fragments[index]);
            }
            trx.show(fragments[index]).commit(); // 添加事务,切换Fragment
        }
        mTabs[currentTabIndex].setSelected(false);
        mTabs[index].setSelected(true);
        currentTabIndex = index;
    }

}
```
.
.
.
两个Fragment

SpcOneFragment
```
public class SpcOneFragment extends Fragment {
    private View rootView;
    private Toolbar mToolBar;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        Log.d(GeneralConst.TAG,"SpcOneFragment --- onCreateView");
        rootView = View.inflate(getActivity(), R.layout.fragment_spc_one, null);
        initView();
        setHasOptionsMenu(true); // 让Fragment的菜单按钮生效
        return rootView;
    }
    private void initView() {
        rootView.findViewById(R.id.mTvOne).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(getActivity(),"SpcOneFragment的Tv点击",Toast.LENGTH_SHORT).show();
            }
        });


        mToolBar = (Toolbar) rootView.findViewById(R.id.mToolBar);
        mToolBar.setTitle("拥抱世界");
        ((AppCompatActivity) getActivity()).setSupportActionBar(mToolBar); // 这样切换后Fragment会失效

        mToolBar.setOverflowIcon(getResources().getDrawable(R.drawable.icon_menu)); // 指定菜单按钮图标
        mToolBar.inflateMenu(R.menu.menu_diy);

        //mToolBar.inflateMenu(R.menu.menu_diy);
        mToolBar.setOnMenuItemClickListener(onMenuItemClick); // 菜单按钮点击监听

        mToolBar.setNavigationIcon(R.drawable.arrow_left); // 返回箭头
        mToolBar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                getActivity().finish();
            }
        });

    }

    // 创建关联菜单
    // 下面这里先clean后inflate这么写是为了避免Fragment和Activity同是带有Toolbar,再加重复的东西
    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        //((AppCompatActivity) getActivity()).getMenuInflater().inflate(R.menu.menu_diy, menu);

        menu.clear();
        inflater.inflate(R.menu.menu_diy, menu);
        super.onCreateOptionsMenu(menu, inflater);


    }

    // 菜单的点击回调
    private Toolbar.OnMenuItemClickListener onMenuItemClick = new Toolbar.OnMenuItemClickListener() {
        @Override
        public boolean onMenuItemClick(MenuItem menuItem) {
            switch (menuItem.getItemId()) {
                case R.id.item_hello:
                    Toast.makeText(getActivity(),"白衣少年",Toast.LENGTH_SHORT).show();
                    break;
                case R.id.item_boy:
                    Toast.makeText(getActivity(),"少年,热闹海岸线",Toast.LENGTH_SHORT).show();
                    break;
            }

            return true;
        }
    };

}
```

布局文件
```
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                xmlns:app="http://schemas.android.com/apk/res-auto"
    >
    <android.support.v7.widget.Toolbar
        android:id="@+id/mToolBar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        android:elevation="4dp"
        android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
        >
    </android.support.v7.widget.Toolbar>

    <TextView
        android:id="@+id/mTvOne"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:layout_gravity="center"
        android:text="SpcOneFragment"
        android:textSize="20dp" />
    
</RelativeLayout>
```

menu文件
```
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      tools:context=".MainActivity" >

    <item android:id="@+id/item_hello"
          android:title="你好"
          android:orderInCategory="90"
          app:showAsAction="never" />

    <item android:id="@+id/item_boy"
          android:title="少年"
          android:orderInCategory="90"
          app:showAsAction="never" />
</menu>
```


另外一个Fragment就不附代码了，类似。

分析阶段：

我们想让每个Fragment都对应有自己的menu，就要注意下面几步
1、在onCreateView里面执行
`
setHasOptionsMenu(true); // 让Fragment的菜单按钮生效
`
而且最好是在所有Toolbar相关操作的前面，不然可能不生效

2、在onCreateOptionsMenu方法里面使用
`
inflater.inflate(R.menu.menu_diy, menu);
`
这样方式去加载menu文件，而不是
`
((AppCompatActivity)getActivity()).getMenuInflater().inflate(R.menu.menu_diy, menu);
`

嗯，大概就是这样啦。

如果你想说为什么我第二个Fragment可以这样子背景、颜色位置，两个Fragment的溢出菜单的样式可以自定义，那么请你看下我的style文件和关于Fragment的布局文件


style文件，重点看AppTheme3和OverflowMenuStyle
```
<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>

    <style name="AppTheme2" parent="Theme.AppCompat.Light.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>

    </style>
    <style name="AppTheme3" parent="Theme.AppCompat.Light.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
        <item name="actionOverflowMenuStyle">@style/OverflowMenuStyle</item>  <!--溢出菜单样式-->

    </style>

    <!-- Toolbar 溢出菜单的样式 -->
    <style name="OverflowMenuStyle" parent="@style/Widget.AppCompat.PopupMenu.Overflow">
        <!-- 是否覆盖锚点，默认为true，即盖住Toolbar -->
        <item name="overlapAnchor">false</item>
        <!-- 弹出层背景颜色 -->
        <item name="android:popupBackground">@color/flow_bg</item>
        <!-- 弹出层垂直方向上的偏移，即在竖直方向上距离Toolbar的距离，值为负则会盖住Toolbar -->
        <item name="android:dropDownVerticalOffset">0dp</item>

        <!-- 弹出层水平方向上的偏移，即距离屏幕左边的距离，负值会导致右边出现空隙 -->
        <item name="android:dropDownHorizontalOffset">-10dp</item>
        <item name="actionMenuTextColor">@color/flow_text_color</item> <!--  指定字体颜色-->
        <item name="android:textColorPrimary">@color/flow_text_color</item> <!--指定之日颜色-->
    </style>


    <!--主页底部导航按钮的样式-->
    <style name="tab_style">
        <item name="android:layout_width">match_parent</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:layout_gravity">center_vertical</item>
        <item name="android:layout_weight">1</item>
        <item name="android:background">@android:color/transparent</item>
        <item name="android:button">@null</item>
        <item name="android:gravity">center</item>
        <item name="android:textColor">@drawable/selector_tab_text_color</item>
        <item name="android:textSize">10sp</item>
    </style>
    
</resources>
```
.
.
.

然后你看一下我第二个Fragment的布局文件


![Paste_Image.png](http://upload-images.jianshu.io/upload_images/1083096-f1e297c6cac9c2da.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

机智如你，必然明了。

本文至此完。

***
代码链接

[git  Link](https://git.oschina.net/amqr/FragmentMenu)
[csdn Link](http://download.csdn.net/detail/icoollike/9694260)