android - FragmentStatePagerAdapter重置第一个 fragment 的内容

当App启动时，它显示第一个片段并准备第二个片段，当我滑动到第二个片段时，它正在准备第三个片段...当我从第二个滑动到第三个片段时，一切都很好，但是当幻灯片1-> 2-> 3-> 2-> 1第一个内容已重设...这里可能是个问题？

import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v7.app.AppCompatActivity;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.view.ViewPager;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class MainActivity extends AppCompatActivity{

    private SectionsPagerAdapter mSectionsPagerAdapter;
    private ViewPager mViewPager;

    FoldersFragment foldersFragment = new FoldersFragment();
    NowPlayingFragment nowPlayingFragment = new NowPlayingFragment();
    EqFragment eqFragment = new EqFragment();

    public ViewPager getMViewPager() {
        return mViewPager;
    }

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

        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

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

        foldersFragment.setNowPlayingFragment(nowPlayingFragment);
        nowPlayingFragment.setFoldersFragment(foldersFragment);
        eqFragment.setMediaPlayer(nowPlayingFragment.mp);
    }

    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

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

    public class SectionsPagerAdapter extends FragmentStatePagerAdapter {

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

        @Override
        public Fragment getItem(int position) {

            switch (position) {
                case 0:
                    System.out.println("0");
                    return foldersFragment;
                case 1:
                    System.out.println("1");
                    return nowPlayingFragment;
                case 2:
                    System.out.println("2");
                    return eqFragment;
            }

            return null;
        }

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

最佳答案

默认的屏幕外限制为1，因此每次您转到下一个片段时，它都会检查是否存在已经离屏的片段，并在您回到该片段时重新启动：

如果您当前位于第3页

1 -> |offset| 2 -> (3) -> 4 -> |offset| 5

因此，如果page 1 and page 5在当前页面之前或之后+偏移量，它将重新启动。

要增加偏移量，您可以致电：

mViewPager.setOffscreenPageLimit(4)