修复了四个android选项卡

Question

我希望我能找到你。我是android新手，一直在努力实现以下目标。一个带有四个固定标签的应用程序，无法滚动。我遇到的挑战只能使三个固定，但是当我添加第四个然后它变得可滚动。这是我想要实现的类似事情。 ＆GT;

这是代码

package com.afroes.testingactionbar;
import android.app.Notification;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBar.Tab;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.TextView;


public class MainActivity extends ActionBarActivity {
    private ActionBar actionBar;


    /**
     * The {@link android.support.v4.view.ViewPager} that will display the object collection.
     */
    ViewPager mViewPager;
    DemoCollectionPagerAdapter mDemoCollectionPagerAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        getWindow().requestFeature(Window.FEATURE_ACTION_BAR_OVERLAY);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        actionBar = getSupportActionBar();
        actionBar.setHomeButtonEnabled(false);
        actionBar.setDisplayShowTitleEnabled(false);
        actionBar.setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));


        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        actionBar.setStackedBackgroundDrawable(new ColorDrawable(
                Color.TRANSPARENT));

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

        mDemoCollectionPagerAdapter =
                new DemoCollectionPagerAdapter(
                        getSupportFragmentManager());


        mViewPager.setAdapter(mDemoCollectionPagerAdapter);
        mViewPager.setOffscreenPageLimit(TRIM_MEMORY_RUNNING_MODERATE);
        mViewPager.setOnPageChangeListener(
                new ViewPager.SimpleOnPageChangeListener() {
                    @Override
                    public void onPageSelected(int position) {
                        // When swiping between pages, select the
                        // corresponding tab.
                        if(position<4)
                        {
                            getSupportActionBar().setSelectedNavigationItem(position);
                        }

                    }
                });

        // Create a tab listener that is called when the user changes tabs.
        ActionBar.TabListener tabListener = new ActionBar.TabListener() {
            public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
                // show the given tab
                mViewPager.setCurrentItem(tab.getPosition());
            }

            public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
                // hide the given tab
            }

            public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
                // probably ignore this event
            }
        };

        // Add 3 tabs, specifying the tab's text and TabListener
        for (int i = 0; i < 4; i++) {
            ActionBar.Tab tab=actionBar.newTab().setTabListener(tabListener);
            tab.setIcon(getIcon(i));
            tab.getIcon().setAlpha(80);
            //tab.getIcon().setAlpha(80);
            actionBar.addTab(tab);
        }

    }

//    @Override
//    public boolean onCreateOptionsMenu(Menu menu) {
//        // Inflate the menu; this adds items to the action bar if it is present.
//        getMenuInflater().inflate(R.menu.menu_main, menu);
//        //return true;
//        return super.onCreateOptionsMenu(menu);
//    }

//    @Override
//    public boolean onOptionsItemSelected(MenuItem item) {
//        // Handle action bar item clicks here. The action bar will
//        // automatically handle clicks on the Home/Up button, so long
//        // as you specify a parent activity in AndroidManifest.xml.
//        int id = item.getItemId();
//
//        //noinspection SimplifiableIfStatement
//        if (id == R.id.action_settings) {
//            return true;
//        }
//
//        return super.onOptionsItemSelected(item);
//    }
    public int getIcon(int position) {
        switch (position) {
            case 0:
                return R.drawable.ic_home;
            case 1:
                return R.drawable.ic_map;
            case 2:
                return R.drawable.ic_notifications;
            case 3:
                return R.drawable.ic_settings;
            default:
                return R.drawable.ic_home;
        }
    }

    // Since this is an object collection, use a FragmentStatePagerAdapter,
// and NOT a FragmentPagerAdapter.
    public class DemoCollectionPagerAdapter extends FragmentStatePagerAdapter {
        public DemoCollectionPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int i) {
            Fragment fragment = new DemoObjectFragment();
            Bundle args = new Bundle();
            // Our object is just an integer :-P
            args.putInt(DemoObjectFragment.ARG_OBJECT, i + 1);
            fragment.setArguments(args);
            return fragment;
        }

        @Override
        public int getCount() {
            return 4;
        }
        @Override
        public CharSequence getPageTitle(int position) {
            return "OBJECT " + (position + 1);
        }
    }

    // Instances of this class are fragments representing a single
// object in our collection.
    public static class DemoObjectFragment extends Fragment {
        public static final String ARG_OBJECT = "object";

        @Override
        public View onCreateView(LayoutInflater inflater,
                                 ViewGroup container, Bundle savedInstanceState) {
            // The last two arguments ensure LayoutParams are inflated
            // properly.
            View rootView = inflater.inflate(
                    R.layout.fragment_home, container, false);
            Bundle args = getArguments();
            ((TextView) rootView.findViewById(android.R.id.text1)).setText(
                    Integer.toString(args.getInt(ARG_OBJECT)));
            return rootView;
        }
    }
}