Android可滚动选项卡+滑动状态当滑动时

Question

我正在尝试制作一个具有多个选项卡的应用程序。对于每个选项卡，我使用不同的碎片。当我翻阅选项卡时，它们中的信息会发生变化。

如何在滑动时保存每个选项卡的状态？

例如代码：

MainActivity.java：

package com.tabs.example;

import java.util.Locale;

import android.graphics.Color;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.PagerTabStrip;
import android.support.v4.view.ViewPager;

public class MainActivity extends FragmentActivity {

    SectionsPagerAdapter mSectionsPagerAdapter;
    ViewPager            mViewPager;

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

        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        PagerTabStrip pagerTabStrip = (PagerTabStrip) findViewById(R.id.pager_tab_strip);
        pagerTabStrip.setBackgroundColor(Color.BLACK);
        pagerTabStrip.setTabIndicatorColor(Color.CYAN);
        pagerTabStrip.setTextColor(Color.WHITE);
    }

    public class SectionsPagerAdapter extends FragmentPagerAdapter {

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {

            Fragment fragment;
            switch (position) {
                case 0:
                    fragment = new Fragment1();
                    break;
                case 1:
                    fragment = new Fragment2();
                    break;
                case 2:
                    fragment = new Fragment3();
                    break;
                default:
                    fragment  = null;
                    break;
            }
            return fragment;

        }

        @Override
        public int getCount() {
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            Locale l = Locale.getDefault();
            switch (position) {
                case 0:
                    return getString(R.string.title_section1).toUpperCase(l);
                case 1:
                    return getString(R.string.title_section2).toUpperCase(l);
                case 2:
                    return getString(R.string.title_section3).toUpperCase(l);
            }
            return null;
        }
    }
}

Fragment1.java:

package com.tabs.example;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Fragment1 extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View root = inflater.inflate(R.layout.fragment1, container, false);

        DateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
        Date date = new Date();
        String time = dateFormat.format(date);

        TextView tv1 = (TextView) root.findViewById(R.id.tv1);
        tv1.setText(time);

        return root;

    }
}

Fragment2.java:

package com.tabs.example;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Fragment2 extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View root = inflater.inflate(R.layout.fragment2, container, false);

        DateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
        Date date = new Date();
        String time = dateFormat.format(date);

        TextView tv2 = (TextView) root.findViewById(R.id.tv2);
        tv2.setText(time);

        return root;

    }
}

Fragment3.java:

package com.tabs.example;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Fragment3 extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View root = inflater.inflate(R.layout.fragment3, container, false);

        DateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
        Date date = new Date();
        String time = dateFormat.format(date);

        TextView tv3 = (TextView) root.findViewById(R.id.tv3);
        tv1.setText(time);

        return root;

    }
}

- Timofey Dmitriev

---

“保存状态”是什么意思？您可以通过设置ViewPagerAdapter来缓存它们：mViewPager.setOffscreenPageLimit(3); - wangyif2

王一凡2，谢谢你！它起作用了。我该如何告诉你“谢谢你”？添加回复并接受他的帮助。 - Timofey Dmitriev

这确实帮助我学习如何通过我的ViewPager启动片段。非常感谢！ - karlstackoverflow

我想在选项卡上方添加标题栏，应该怎么做？ - Araju

@Timofey Dmitriev - 我已经找到了解决方案。 - Araju

Answer 1

您可以通过设置ViewPagerAdapter来缓存它们，如下所示：

mViewPager.setOffscreenPageLimit(3);

- wangyif2

---

我想在选项卡上方添加标题部分，我应该怎么做？ - Araju