它必须是简单的东西.
我正在展示大部分代码.错误在下一节中.

public class MainActivity extends FragmentActivity implements
    ActionBar.TabListener {

public static final int TAB_COUNT = 3;
public static InputMethodManager inputManager;

SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;

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

    mSectionsPagerAdapter = new SectionsPagerAdapter(
            getSupportFragmentManager());

    // Set up the action bar.
    final ActionBar actionBar = getActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

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

    // When swiping between different sections,select the corresponding
    // tab.
    mViewPager
            .setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
                @Override
                public void onPageSelected(int position) {
                    actionBar.setSelectedNavigationItem(position);
                }
            });

    // For each of the sections in the app,add a tab to the action bar.
    for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {

        actionBar.addTab(actionBar.newTab()
                .setText(mSectionsPagerAdapter.getPageTitle(i))
                .setTabListener(this));
    }

    // To control keyboard pop-up
    inputManager = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);

}
    @Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main,menu);
    return true;
}

@Override
public void onTabUnselected(ActionBar.Tab tab,FragmentTransaction fragmentTransaction) {
}

@Override
public void onTabSelected(ActionBar.Tab tab,FragmentTransaction fragmentTransaction) {
    // When the given tab is selected,switch to the corresponding page in
    // the ViewPager.
    mViewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabReselected(ActionBar.Tab tab,FragmentTransaction fragmentTransaction) {
}

这是我的错误所在.
getItem的case 1,Type mismatch：无法从MainActivity.HistoryFragment转换为Fragment.它告诉我要么将方法返回类型更改为HistoryFragment,要么将newInstance()的返回类型更改为Fragment.哪里我也做不到.我见过的其他例子与我的代码几乎相同.我曾经尝试过,不经过论证.

public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int i) {
        switch (i) {
        case 0:
            Fragment tipCalc = new TipCalcFragment();
            return tipCalc;
        case 1:
            // Fragment history = new HistoryFragment();
            return HistoryFragment.newInstance(i); //ERROR HERE
        case 2:
            Fragment stats = new StatsFragment();
            return stats;
        }
        return null;
    }

我的HistoryFragment扩展了ListFragment.最后,它不会从String []值中提取,而是从数据库资源中提取.我只是想先设置一个结构,然后看看/播放布局.

public static class HistoryFragment extends ListFragment {
    // public HistoryFragment() {
    // }

    String[] values = new String[] { ... };

    static HistoryFragment newInstance(int num) {
        HistoryFragment history = new HistoryFragment();

        Bundle args = new Bundle();
        args.putInt("num",num);

        history.setArguments(args);

        return history;
    }

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

        View view = inflater.inflate(R.layout.history,container,false);

        return view;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        setListAdapter(new ArrayAdapter<String>(getActivity(),android.R.layout.simple_list_item_1,android.R.id.text1,values));
    }
}