android fragment replace back and forth

Question

I have only one Activity:

package com.duandianer.ddr_v2.module.login.activity;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTabHost;
import android.support.v4.app.FragmentTransaction;
import android.util.Log;
import android.widget.TabWidget;

import com.duandianer.ddr_v2.R;
import com.duandianer.ddr_v2.common.activity.BaseActivity;
import com.duandianer.ddr_v2.common.fragment.BaseFragment;
import com.duandianer.ddr_v2.module.login.fragment.FindPasswdFragment;
import com.duandianer.ddr_v2.module.login.fragment.LoginFragment;

public class LoginActivity extends BaseActivity {
    private static int FRAGMENT_ID = R.id.login_view_bottom_fragment;
    private FragmentManager mFragmentManager;
    private FragmentTransaction mFragmentTransaction;

    @Override

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

        mFragmentManager = getSupportFragmentManager();
        replaceFragment(LoginFragment.class);
    }


    public void replaceFragment(Class<? extends BaseFragment> C) {
        mFragmentTransaction = mFragmentManager.beginTransaction();
        Fragment old = mFragmentManager.findFragmentById(FRAGMENT_ID);
        Log.d("ddr", old + "");
        try {
            if (old == null)
                mFragmentTransaction.add(FRAGMENT_ID, C.newInstance());
            else if (!C.isInstance(old)) {
                mFragmentTransaction.replace(FRAGMENT_ID, C.newInstance());
            }
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        mFragmentTransaction.commit();
    }
}

and I use replaceFragment() to replace fragment

the login_view.xml is:

<?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">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="@dimen/login_view_top_background_height">

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:contentDescription="@string/login_view_login_background_describe"
            android:scaleType="centerCrop"
            android:src="@mipmap/login_view_login_background" />

        <ImageButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:layout_alignParentTop="true"
            android:layout_marginRight="@dimen/login_view_top_close_button_margin_top"
            android:layout_marginTop="@dimen/login_view_top_close_button_margin_right"
            android:background="#00000000"
            android:contentDescription="@string/login_view_close_button_describe"
            android:src="@mipmap/login_view_close_button" />
    </RelativeLayout>

    <FrameLayout
        android:id="@+id/login_view_bottom_fragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#FFFFFF" />

</LinearLayout>

then I replace fragments between LoginFragment and FindPasswdFragment

the LoginFragment is:

package com.duandianer.ddr_v2.module.login.fragment;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentTabHost;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TabHost;
import android.widget.TabWidget;

import com.duandianer.ddr_v2.R;
import com.duandianer.ddr_v2.common.fragment.BaseFragment;

import java.lang.ref.SoftReference;
import java.util.ArrayList;

public class LoginFragment extends BaseFragment {
    private final ArrayList<Fragment> Fragments = new ArrayList<>();
    private final ArrayList<CharSequence> Titles = new ArrayList<>();
    private SoftReference<View> mView;

    private TabLayout mTabLayout;
    private ViewPager mViewPager;

    private ViewPagerAdapter mAdapter;

    private final LoginFragment_LoginFragment loginFragment_loginFragment =
            new LoginFragment_LoginFragment();

    private final LoginFragment_RegisterFragment loginFragment_registerFragment =
            new LoginFragment_RegisterFragment();

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        if (mView == null || mView.get() == null) {
            View view = inflater.inflate(R.layout.login_view_login_fragment, null);
            mView = new SoftReference<>(view);

            mAdapter = new ViewPagerAdapter(getActivity().getSupportFragmentManager());

            Fragments.add(loginFragment_loginFragment);
            Fragments.add(loginFragment_registerFragment);

            Titles.add("登录");
            Titles.add("注册");

            mTabLayout = (TabLayout) mView.get().findViewById(R.id.login_view_bottom_fragment_tab);
            mViewPager = (ViewPager) mView.get().findViewById(R.id.login_view_bottom_fragment_viewpager);

            mTabLayout.setTabGravity(TabLayout.GRAVITY_FILL);

            mViewPager.setAdapter(mAdapter);

            mTabLayout.setupWithViewPager(mViewPager);

            Log.d("ddr", "create login");
        }

        ViewGroup parent = (ViewGroup) mView.get().getParent();
        if (parent != null)
            parent.removeView(mView.get());
        return mView.get();
    }


    @Override
    public void onDestroy() {
        super.onDestroy();
        mView = null;
        mTabLayout = null;
        mViewPager = null;

        Log.d("ddr", "destroy login");
    }

    private class ViewPagerAdapter extends FragmentPagerAdapter {
        public ViewPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            return Fragments.get(position);
        }

        @Override
        public int getCount() {
            return Fragments.size();
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return Titles.get(position);
        }
    }
}

the FindPasswdFragment is:

package com.duandianer.ddr_v2.module.login.fragment;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

import com.duandianer.ddr_v2.R;
import com.duandianer.ddr_v2.common.fragment.BaseFragment;
import com.duandianer.ddr_v2.module.login.activity.LoginActivity;
import com.duandianer.ddr_v2.module.login.controllers.LoginController;

import java.lang.ref.SoftReference;

public class FindPasswdFragment extends BaseFragment {
    private SoftReference<View> mView;

    private LoginController mController;

    private Button mReturn;

    private final OnClickListenerImpl onClickListener = new OnClickListenerImpl();

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        if (mView == null || mView.get() == null) {
            mView = new SoftReference<>(inflater.inflate(R.layout.login_view_find_passwd_fragment, null));

            mReturn = (Button) mView.get().findViewById(R.id.login_view_bottom_fragment_find_passwd_button_return);
            mReturn.setOnClickListener(onClickListener);

            mController = LoginController.SingTon.INSTANCE.getInstance((LoginActivity) getActivity());
        }
        ViewGroup parent = (ViewGroup) mView.get().getParent();
        if (parent != null)
            parent.removeView(mView.get());
        return mView.get();
    }

    private class OnClickListenerImpl implements View.OnClickListener {
        @Override
        public void onClick(View v) {
            if (v == mReturn) {
                mController.replaceFragment(LoginFragment.class);
            }
        }
    }
}

the LoginFragment use a viewpager and it contain two other fragments

So,the problem is: when I using replaceFragment(FindPasswdFragment.class),it can jump from LoginFragment to FindPasswdFragment,and it works good. But then,when I using replaceFragment(LoginFragment.class) to jump from FindPasswdFragment to LoginFragment,a few problems have come up: the two sub-fragments in LoginFragment are not visiable,only have two tabs.

And I spent two days to solve it,but i failed.I do not know why the two sub-fragments will not visiable. But I discovered that the onCreateView and onDestroy of two sub-fragments both not called.

So...can you help me ??

score 0 · Accepted Answer · answered May 29 '17 at 13:47

0

try replacing on your login fragment:

mAdapter = new ViewPagerAdapter(getActivity().getSupportFragmentManager());

with

mAdapter = new ViewPagerAdapter(getChildFragmentManager());

getChildFragmentManager() should be used to handle fragments inside fragments.

answered May 29 '17 at 13:47

Jonathan Aste

1,764
1
13
20

getChildFragmentManager() is the FragmentManager used inside fragments. And getFragmentManager() or getSupportFragmentManager() are used inside activities. To see a full explanation about this you can check this answer: https://stackoverflow.com/a/14775322/5658915 or visit the official android doc about fragments: https://developer.android.com/reference/android/app/Fragment.html - https://developer.android.com/reference/android/app/Fragment.html#getChildFragmentManager(). Hope it helps you ! – Jonathan Aste May 30 '17 at 13:22

android fragment replace back and forth

1 Answers1