java - 如何从另一个 fragment 更改 ViewPager fragment ？不做新事

Question

此应用程序是一份调查问卷。

我使用 ViewPager 来托管 fragment 。

当用户到达最后一个屏幕 EndingQuestionsFragment 时，他们有一个按钮，按下该按钮会将他们带到主屏幕(对我的问题来说并不重要)。

如果有一个未回答的问题，当单击该按钮时，应该将它们带到包含未回答的问题的 fragment 。

我用过:

MainActivity parent = (MainActivity) getActivity();
parent.setPagerFragment(0);

在 setOnClickListener 内。

但是，当单击该按钮时，给出的任何答案都会被重置。 (单选按钮已重置)。

如何在 fragment 中导航而不丢失输入？

FragmentCommunicator.java

package com.example.zdroa.testinggrounds;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;

import com.example.zdroa.testinggrounds.Question_Fragments.AnxiousQuestionsFragment;
import com.example.zdroa.testinggrounds.Question_Fragments.DependentQuestionsFragment;
import com.example.zdroa.testinggrounds.Question_Fragments.DepressiveQuestionsFragment;
import com.example.zdroa.testinggrounds.Question_Fragments.EndingQuestionsFragment;
import com.example.zdroa.testinggrounds.Question_Fragments.HistrionicQuestionsFragment;
import com.example.zdroa.testinggrounds.Question_Fragments.InitializerFragment;
import com.example.zdroa.testinggrounds.Question_Fragments.NarcissistQuestionsFragment;
import com.example.zdroa.testinggrounds.Question_Fragments.ObsessiveQuestionsFragment;
import com.example.zdroa.testinggrounds.Question_Fragments.ParanoidQuestionsFragment;
import com.example.zdroa.testinggrounds.Question_Fragments.SchizoidQuestionsFragment;


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

    @Override
    public Fragment getItem(int position) {
        switch (position){
            case 0:
                return new InitializerFragment();
            case 1:
                return new AnxiousQuestionsFragment();
            case 2:
                return new ParanoidQuestionsFragment();
            case 3:
                return new HistrionicQuestionsFragment();
            case 4:
                return new ObsessiveQuestionsFragment();
            case 5:
                return new NarcissistQuestionsFragment();
            case 6:
                return new SchizoidQuestionsFragment();
            case 7:
                return new DepressiveQuestionsFragment();
            case 8:
                return new DependentQuestionsFragment();
            case 9:
                return new EndingQuestionsFragment();
        }
        return null;
    }

    @Override
    public int getCount() {
        return 10;
    }
}

MainActivity.java

package com.example.zdroa.testinggrounds;

import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;

import com.example.zdroa.testinggrounds.Question_Fragments.AnxiousQuestionsFragment;

public class MainActivity extends AppCompatActivity {

    public static String PERSON_TYPE;
    ViewPager viewPager;
    public static FragmentCommunicator communicator;

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

        viewPager = (ViewPager) findViewById(R.id.vpQuestionsActivity);
        communicator = new FragmentCommunicator(getSupportFragmentManager());
        viewPager.setAdapter(communicator);
        viewPager.setCurrentItem(0);

        int anxious_result = new AnxiousQuestionsFragment().getResult();
        if (anxious_result != 0){
            PERSON_TYPE = "Anxious person";
        }

    }

    public String getPersonType() {
        return PERSON_TYPE;
    }

    public void setPagerFragment(int a){
        viewPager.setCurrentItem(a);
    }    
}

EndingQuestionsFragment.java

package com.example.zdroa.testinggrounds.Question_Fragments;

import android.os.Build;
import android.os.Bundle;
import android.support.annotation.RequiresApi;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

import com.example.zdroa.testinggrounds.MainActivity;
import com.example.zdroa.testinggrounds.R;

public class EndingQuestionsFragment extends Fragment {

    public EndingQuestionsFragment() {
        // Required empty public constructor
    }


    @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN_MR1)
    @Override
    public View onCreateView(final LayoutInflater inflater, final ViewGroup container,
                             Bundle savedInstanceState) {
        final View view = inflater.inflate(R.layout.fragment_ending_questions, container, false);

        Button button1 = (Button) view.findViewById(R.id.bGotoMainAreaActivity);
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MainActivity parent = (MainActivity) getActivity();
                parent.setPagerFragment(0);
            }
        });



        return view;
    }

}

fragment_ending_questions.xml

<RelativeLayout 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="#fefefe"
    android:padding="16dp"
    tools:context="com.example.zdroa.testinggrounds.Question_Fragments.AnxiousQuestionsFragment">


    <TextView
        android:id="@+id/ending_tv_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="The End"
        android:textAlignment="center"
        android:textColor="#000"
        android:textSize="30sp"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/ending_tv_message"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/ending_tv_title"
        android:layout_marginTop="30dp"
        android:text="Now that you have answered all the questions please click the Finish button.\n\nIf any questions have been left unanswered you will be taken back to the screen with the missing answeres. Your other answeres will not be affected."
        android:textAlignment="center"
        android:textColor="#000"
        android:textSize="20sp" />

    <Button
        android:id="@+id/bGotoMainAreaActivity"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_marginTop="30dp"
        android:text="Finish" />

</RelativeLayout>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    tools:context=".MainActivity">

    <android.support.v4.view.ViewPager
        android:id="@+id/vpQuestionsActivity"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    </android.support.v4.view.ViewPager>

</RelativeLayout>

Answer 1

在 FragmentActivity 中使用 `ViewPager.setOffscreenPageLimit()原因？？您使用的默认 fragment 分页器适配器，每次您滑动时它都会销毁并重新创建 fragment ，使用此代码您告诉它不要破坏先前加载的 fragment 的初始 fragment 状态

ViewPager pager = (ViewPager) findViewById(R.id.viewPager);
pager.setOffscreenPageLimit(10); // i assumed there are 10 fragments in total