如何在 ViewPage 中从 Activity 移动到 Fragment？ 未找到片段 ID 的视图

Question

I just started learning android. I have a Activity class and I want to redirects it to a fragment in ViewPage of a Navigation bar? I try many ways but it don't work. I hope to help:.! My code: There is a MainActivity.java has a ViewPager and BottomNavigationView

public class MainActivity extends AppCompatActivity {
    BottomNavigationView navigationView;
    ViewPager mViewPager;

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        navigationView = findViewById(R.id.nav);
        mViewPager = findViewById(R.id.view_pager);

        setUpViewPager();
        navigationView.setOnNavigationItemReselectedListener(new BottomNavigationView.OnNavigationItemReselectedListener() {
            @Override
            public void onNavigationItemReselected(@NonNull MenuItem item) {
                if(item.getItemId()== R.id.cld){
                    mViewPager.setCurrentItem(0);
                } else if(item.getItemId()== R.id.tdl){
                    mViewPager.setCurrentItem(1);
                }else if(item.getItemId()== R.id.dnr){
                    mViewPager.setCurrentItem(2);
                }else if(item.getItemId()== R.id.us){
                    mViewPager.setCurrentItem(3);
                }

            }
        });

        try {
            Field field = CursorWindow.class.getDeclaredField("sCursorWindowSize");
            field.setAccessible(true);
            field.set(null, 100 * 1024 * 1024); //the 100MB is the new size
        } catch (Exception e) {

                e.printStackTrace();

        }
    }

    private void setUpViewPager() {
        ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager(), FragmentStatePagerAdapter.BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
        mViewPager.setAdapter(viewPagerAdapter);
        mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {
                switch (position){
                    case 1:
                        navigationView.getMenu().findItem(R.id.tdl).setChecked(true);
                        break;
                    case 2:
                        navigationView.getMenu().findItem(R.id.dnr).setChecked(true);
                        break;
                    case 3:
                        navigationView.getMenu().findItem(R.id.us).setChecked(true);
                        break;
                    default: navigationView.getMenu().findItem(R.id.cld).setChecked(true);
                        break;

                }
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
    }


}

ViewPageApdater class

public class ViewPagerAdapter extends FragmentStatePagerAdapter {
    public ViewPagerAdapter(@NonNull  FragmentManager fm, int behavior) {
        super(fm, behavior);
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        switch (position){
            case 1: return new ListTodo();
            case 2: return  new dinary_form();
            case 3: return  new UserInfor();
            case 0:
            default: return new Calendar();
        }
    }

    @Override
    public int getCount() {
        return 5;
    }
}

And Activity class I want to move and I have a problem: java.lang.IllegalArgumentException: No view found for id 0x7f0a01d3 (com.example.projectminibook:id/view_pager) for fragment ListTodo{bbdabd4 (d10d7649-01eb-4b76-8342-fbf47138d234) id=0x7f0a01d3}

I take id/view_paper from id of ViewPager layout in activitymain. I dont know where wrong

public class AddTodo extends AppCompatActivity {
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Button btnCancel = findViewById(R.id.btnCancel);
        btnSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               ListTodo fragment = new ListTodo();
                FragmentManager fragmentManager = getSupportFragmentManager();
                FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
                fragmentTransaction.add(R.id.view_pager,fragment);
                fragmentTransaction.commit();
            }
        });
    }
}

ListTodo.java

public class ListTodo extends Fragment{
  //mycode
}

I hope you can help me. Thank you very much

Answer 1

Just try below code in onNavigationItemSelectedListener

---

@Override
        public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
            Fragment fragment = null;
            switch (menuItem.getItemId()) {
                case R.id.cld:
                    viewPager.setCurrentItem(0);
                    break;

                case R.id.tdl:
                    viewPager.setCurrentItem(1);
                    break;

                case R.id.dnr:
                    viewPager.setCurrentItem(2);
                    break;

                case R.id.us:
                    viewPager.setCurrentItem(3);
                    break;

                default:
                    viewPager.setCurrentItem(0);
                    break;
            }
            return true;
        }

---

I think your problem will go after update this code in your MainActivity . Happy Coding;)

---

UPDATE

the upper code also has minor changes & for the viewPager please edit your code of onPageSelected() method with below code

 @Override
            public void onPageSelected(int position) {
                switch (position){
                    case 1:
                        NavigationView.setSelectedItemId(R.id.tdl);
                        break;
                    case 2:
                        NavigationView.setSelectedItemId(R.id.dnr);
                        break;
                    case 3:
                        NavigationView.setSelectedItemId(R.id.us);
                        break;
                    default: 
                        NavigationView.setSelectedItemId(R.id.cld);
                        break;

                }
            }

---

Answer 2

you are not directly navigate to that fragment which is in the another activity. that's why you are getting this illegalArgumentException error.

1). you have to navigate to that activity first.

---

2). you have to check that the navigated activity is where come from. for this you can use Intent's put extra method.

---

3). if the intent.put extra has any value then you have to navigate from one fragment to another. In your case, you have to navigate from calender fragment to ListTodo fragment in main activity.

public class AddTodo extends AppCompatActivity {
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Button btnCancel = findViewById(R.id.btnCancel);
        btnSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               startActivity(new Intent(activity, MainActivity.class).putExtra("from","AddTodo"));
            }
        });
    }
}

---

& in MainActivity 's onCreate method you have to code like this.

---

String comeFrom = getIntent().getStringExtra("from");
if (!(comeFrom.equals("") || comeFrom.isEmpty()) && comeFrom.equals("AddTodo")){
    viewPager.setCurrentItem(1); //because your list todo fragment is 2nd fragment in your viewpager
}