我有一个mainactivity和一个按钮“add”，应该发送到第二个Activity（它有一个tablayout和fragments）。下面的代码是launchsecondactivty（）方法。

Intent intent = new Intent(this, SecondActivity.class);
        String et_title = title.getText().toString();
        String et_room = room.getText().toString();
        String et_code = code.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, et_title);
        intent.putExtra(EXTRA_MESSAGE, et_room);
        intent.putExtra(EXTRA_MESSAGE, et_code);
        startActivityForResult(intent, ADD_REQUEST);

这是我的第二个activity oncreate（）方法。

super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        Intent intent = getIntent();

这将非常有效。但当我为片段添加代码时，

tabLayout = (TabLayout) findViewById(R.id.tab_days);
        tabMon = (TabItem) findViewById(R.id.itm_mon);
        tabTue = (TabItem) findViewById(R.id.itm_tue);
        tabWed = (TabItem) findViewById(R.id.itm_wed);
        tabThu = (TabItem) findViewById(R.id.itm_thu);
        tabFri = (TabItem) findViewById(R.id.itm_fri);
        tabSat = (TabItem) findViewById(R.id.itm_sat);
        tabSun = (TabItem) findViewById(R.id.itm_sun);
        viewPager = (ViewPager) findViewById(R.id.viewpager);

        pagerAdapter = new com.example.timetable2.PagerAdapter(getSupportFragmentManager(), tabLayout.getTabCount());
        viewPager.setAdapter(pagerAdapter);

        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
                if(tab.getPosition() == 0) {
                    pagerAdapter.notifyDataSetChanged();
                }else if(tab.getPosition() == 1) {
                    pagerAdapter.notifyDataSetChanged();
                }else if(tab.getPosition() == 2) {
                    pagerAdapter.notifyDataSetChanged();
                }else if(tab.getPosition() == 3) {
                    pagerAdapter.notifyDataSetChanged();
                }else if(tab.getPosition() == 4) {
                    pagerAdapter.notifyDataSetChanged();
                }else if(tab.getPosition() == 5) {
                    pagerAdapter.notifyDataSetChanged();
                }else if(tab.getPosition() == 6){
                    pagerAdapter.notifyDataSetChanged();
                }
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {

            }
        });

        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    }

这是事故日志。

2020-12-13 02:16:47.064 6449-6449/? E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.timetable2, PID: 6449
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.timetable2/com.example.timetable2.SecondActivity}: java.lang.ClassCastException: androidx.viewpager2.widget.ViewPager2 cannot be cast to androidx.viewpager.widget.ViewPager
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3654)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3806)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2267)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:237)
        at android.app.ActivityThread.main(ActivityThread.java:8167)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
     Caused by: java.lang.ClassCastException: androidx.viewpager2.widget.ViewPager2 cannot be cast to androidx.viewpager.widget.ViewPager
        at com.example.timetable2.SecondActivity.onCreate(SecondActivity.java:36)
        at android.app.Activity.performCreate(Activity.java:7963)
        at android.app.Activity.performCreate(Activity.java:7952)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1307)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3629)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3806) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2267) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:237) 
        at android.app.ActivityThread.main(ActivityThread.java:8167) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100) 

这不管用了。请帮助我的项目。这里是初学者((