Android-實現切換Fragment頁功能

場景：使用Fragment實現切頁。

類結構：

　　

一：Activity

Activity中使用getSupportFragmentManager().beginTransaction()來填充一個Fragment（管理用的FragmentA）

Activity部分代碼：

FragmentA fragment = FragmentA.newInstant(null);
getSupportFragmentManager().beginTransaction().add(R.id.f_tab_fragment,fragment).commit();

XML:

            <FrameLayout
                android:id="@+id/fl_container"
                android:layout_width="match_parent"
                android:layout_above="@+id/f_tab_fragment"
                android:layout_height="match_parent"/>

            <FrameLayout
                android:id="@+id/f_tab_fragment"
                android:layout_width="match_parent"
                android:layout_height="52dp"
                android:layout_alignParentBottom="true"/>

 

二：FragmentA

加載一個主FragmentA，做爲管理其它子葉片FragmentX。

如今好比有兩個子葉片FragmentB、FragmentC.

FragmentA 使用FragmentManager和FragmentTransaction管理FragmentB、FragmentC的切換 

FragmentA代碼:

public class FragmentA extends BaseFragment {

    private static final String TAB_HOME = com.timediffproject.module.home.MyMainFragment.class.getName();

    private static final String TAB_TEST = com.timediffproject.module.home.TestFragment.class.getName();

    private BaseFragment mLastShowFragment;

    private static TabFragment fragment;

    public static TabFragment newInstant(Bundle bundle){
        if (fragment == null){
            fragment = new TabFragment();
            fragment.setArguments(bundle);
        }
        return fragment;
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initTabInfo();

    }

    private void initTabInfo(){
        FragmentManager fm = getFragmentManager();
        if (fm == null){
            return;
        }
        FragmentTransaction ft = fm.beginTransaction();

        BaseFragment home = (BaseFragment) fm.findFragmentByTag(TAB_HOME);
        if (home != null){
            ft.hide(home);
        }

        BaseFragment test = (BaseFragment) fm.findFragmentByTag(TAB_TEST);
        if (test != null){
            ft.hide(test);
        }

        ft.commit();

    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_tab,container,false);
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        view.findViewById(R.id.btn_change_home).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                switchTo(TAB_HOME,null);
            }
        });
        view.findViewById(R.id.btn_change_test).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                switchTo(TAB_TEST,null);
            }
        });
        switchTo(TAB_HOME,null);
    }

    //切換Fragment的方式（FragmentB、FragmentC）
    //tab爲Fragment的類名（如：FragmentB.class.getName()）
    //R.id.fl_container是在Activity的佈局裏，不是在FragmentA的佈局裏
    private void switchTo(String tab, Bundle bundle){

        //初始化管理Fragment的類
        FragmentManager fm = getFragmentManager();
        if (fm == null){
            return;
        }
        FragmentTransaction ft = fm.beginTransaction();

        //從FragmentManager裏尋找類名爲tab的Fragment
        BaseFragment fragment = (BaseFragment)fm.findFragmentByTag(tab);
        if (fragment == null){
            fragment = (BaseFragment) Fragment.instantiate(getActivity(),tab);
            fragment.setArguments(bundle);
            ft.add(R.id.fl_container,fragment,tab);
        }else{
            ft.show(fragment);
        }
        //隱藏如今正顯示的Fragment
        if (mLastShowFragment != null) {
            ft.hide(mLastShowFragment);
        }
        //記錄最後點擊的Fragment
        mLastShowFragment = fragment;

        ft.commitAllowingStateLoss();


    }


}

 

XML:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="match_parent"
    android:layout_height="52dp">

    <Button
        android:id="@+id/btn_change_home"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="切換home"
        />

    <Button
        android:id="@+id/btn_change_test"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="切換test"
        />

</LinearLayout>

 

 三：FragmentX(FragmentB、FragmentC)

子頁的邏輯根據具體業務本身定義，實現與通常Fragmeng同樣

例如：

public class TestFragment extends BaseFragment {

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {return inflater.inflate(R.layout.fragment_test,container,false);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }

}

 

到這裏，就能夠簡單的實現-用底部Tab切換Fragment實現切頁的功能

 附圖：

   

 

PS:實現過程當中出現的錯誤 

　　java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.

正確方式： 有關的fragment的初始化佈局應該加上false，與父類佈局創建關係。

緣由：不加的話這個inflater出來的view系統會綁定一個未知父類，這時候當你把這個fragment又做爲子頁綁定給Activity或者另外一個fragment時，就會出現以上錯誤。

@Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        //這裏正確的寫法是:
        //return inflater.inflate(R.layout.fragment_test,container,false);
        return inflater.inflate(R.layout.fragment_test,container);
     }