Android Scrollable Tabs + 滑动时的滑动状态

Question

我正在尝试制作一个包含多个选项卡的应用程序。对于每个选项卡，我使用不同的片段。当我浏览标签时，它们中的信息正在发生变化。

如何在滑动时保存每个标签的状态？

代码示例：

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;

    }
}

Answer 1

您可以通过像这样设置 ViewPagerAdapter 来缓存它们：

mViewPager.setOffscreenPageLimit(3);