在片段活动中更改选项卡的标题

Question

我想在选项卡式活动中更改选项卡的标题。 当前使用以下代码，我可以切换到选项卡，但是在到达通知时无法更改选项卡标题。

如何更改标签的标题。

ViewPager viewPager = (ViewPager) AllTabs.mViewPager.findViewById(R.id.container);
                    int currentTab = viewPager.getCurrentItem();
                    viewPager.setCurrentItem(1);

上面的代码有助于更改或切换到mytab。 尝试下面的代码检查选项卡的标题

PagerAdapter pagerAdapter = new PagerAdapter() {
                            @Override
                            public int getCount() {
                                return 0;
                            }

                            @Override
                            public boolean isViewFromObject(View view, Object object) {
                                return false;
                            }
                        };
                        Log.e("ServerManager_Title",pagerAdapter.getPageTitle(1).toString());
                        pagerAdapter.notifyDataSetChanged();

但是由于pagerAdapter没有与任何选项卡相关联，因此在调用任何方法时都会引发NullPointerException。

12-22 11:27:37.049 20448-20448/com.moodoff E/AndroidRuntime: FATAL EXCEPTION: main
                                                             Process: com.moodoff, PID: 20448
                                                             java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.String java.lang.CharSequence.toString()' on a null object reference
                                                                 at com.moodoff.helper.ServerManager$3.run(ServerManager.java:199)
                                                                 at android.os.Handler.handleCallback(Handler.java:815)
                                                                 at android.os.Handler.dispatchMessage(Handler.java:104)
                                                                 at android.os.Looper.loop(Looper.java:207)
                                                                 at android.app.ActivityThread.main(ActivityThread.java:5776)
                                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:679)

我的代码：在ServerManager.java文件中

final Activity currActivity = (Activity)context;
        NotificationCompat.Builder builder =
            new NotificationCompat.Builder(currActivity)
                    .setSmallIcon(R.drawable.btn_dedicate)
                    .setColor(001500)
                    .setContentTitle("MoodOff")
                    .setContentText(UserDetails.getUserName()+ "!! You got new notifications!!");

        Intent notificationIntent;
        if(currActivity==null){
            notificationIntent = new Intent(currActivity, Start.class);
            notificationIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
        }
        else{
            currActivity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    //Toast.makeText(context,"Hi New one",Toast.LENGTH_SHORT).show();
                    //designNotPanel(1);
                    ViewPager viewPager = (ViewPager) AllTabs.mViewPager.findViewById(R.id.container);
                    int currentTab = viewPager.getCurrentItem();
                    viewPager.
                    viewPager.getAdapter().notifyDataSetChanged();

                }
            });
            notificationIntent = new Intent(currActivity, NotificationFragment.class);
            notificationIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
        }
        PendingIntent contentIntent = PendingIntent.getActivity(currActivity, 0, notificationIntent,
            PendingIntent.FLAG_CANCEL_CURRENT);
        builder.setContentIntent(contentIntent);
        builder.setAutoCancel(true);
}

在AllTabs.java中，它承载所有选项卡，或者是具有所有选项卡的主要活动，公共类AllTabs扩展了AppCompatActivity实现的ViewPager.OnPageChangeListener {

/**
 * The {@link android.support.v4.view.PagerAdapter} that will provide
 * fragments for each of the sections. We use a
 * {@link FragmentPagerAdapter} derivative, which will keep every
 * loaded fragment in memory. If this becomes too memory intensive, it
 * may be best to switch to a
 * {@link android.support.v4.app.FragmentStatePagerAdapter}.
 */
private SectionsPagerAdapter mSectionsPagerAdapter;

/**
 * The {@link ViewPager} that will host the section contents.
 */
//private ViewPager mViewPager;
public static ViewPager mViewPager;


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

    // Create the adapter that will return a fragment for each of the three
    // primary sections of the activity.
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());


    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(mViewPager);

    //Request all the dangerous permissions over here

}

@Override
public void onPageScrollStateChanged(int state) {

}

@Override
public void onPageSelected(int position) {

}

@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

}

阿美的做法正确吗？ 通知到达时，我想在第二个选项卡上显示一个计数（数字）（与我拥有的三个选项卡中的哪个选项卡无关），该数字是动态的，因此一旦出现通知，我就需要计算并显示，即根据动态计数将第二个选项卡的标题更改为新标题。

Answer 1

1.activity应该实现一个OnPageChangeListener

2.创建您的ViewPager

3.你可以使用viewPager.setOnPageChangeListener(this)

4。

@Override
        public abstract void onPageSelected(int position) {
            setTitle(getTitleFromPosition(position));
        }

然后pagerAdapter.getPageTitle(1).toString()不会为null

看这里

如果ViewPager.setOnPageChangeListener因为已被弃用而无法运行，请改用ViewPager.addOnPageChangeListener 。

例如，

viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {

        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });

Answer 2

作为@Charuka，这也是可能的，您也可以这样做。

viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);

tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);

这是设置ViewPager适配器的方法。

private void setupViewPager(ViewPager viewPager)
{
    try
    {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.addFrag(new FragmentGeneral(), "GENERAL");
        adapter.addFrag(new FragmentInterests(), "INTERESTS");
        adapter.addFrag(new FragmentAlert(), "ALERTS");
        adapter.addFrag(new FragmentSocial(), "SOCIAL");
        viewPager.setAdapter(adapter);
    }
    catch (Exception e)
    {
        e.printStackTrace();
    }
}

现在创建ViewPagerAdapter类，该类可以处理您的片段和Tab标题

private class ViewPagerAdapter extends FragmentPagerAdapter
    {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

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

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }

        public void addFrag(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public CharSequence getPageTitle(int position) {

            //here you can set your custom title by using position 
            if (position==1)
                return "Title";
            else
                return mFragmentTitleList.get(position);
        }
    }

欲了解更多详情请查看这个和这个 。