如何用viewPager修复“一次活动中的3段需要验证前两页然后可能转到第三页”

Question

我想要创建一个createOrderActivity，其中有三个片段，如服务信息、ScheduleInfo、确认

服务信息片段有editText如果单击NextButton(位于CreateOrderActivity)，首先检查验证editText。然后移动ScheduleFragment页面。如果前两页验证正常，然后移动到确认片段页。

下面是FragmentViewpagerAdapter类

public class FragmentViewPagerAdapter extends FragmentPagerAdapter {

private final List<Fragment> fragmentList = new ArrayList<>();
private final List<String> fragmentTitleList = new ArrayList<>();

public FragmentViewPagerAdapter(FragmentManager manager) {
    super(manager);
}

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

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

public void addFragment(Fragment fragment, String title) {
    fragmentList.add(fragment);
    fragmentTitleList.add(title);
}

@Override
public CharSequence getPageTitle(int position) {
    return fragmentTitleList.get(position);
}

}

在CreateOrderActivity类中

        @Override
        public void onPageSelected(int position) {

            boolean checkSch= false;
            if (position == 1) {

                ServiceInfoFragment serviceInfoFragment = new ServiceInfoFragment();

                //checking validation from ServiceInfoFragment fragment Class
                if (serviceInfoFragment.checkServiceValidation()) {


                    checkSch = true;
                    //Toast.makeText(CreateOrderActivity.this, "Validation okay", Toast.LENGTH_SHORT).show();
                }else {
                    checkSch = false;
                   // Toast.makeText(CreateOrderActivity.this, "Please check validation", Toast.LENGTH_SHORT).show();
                    pagerCreateOrder.setCurrentItem(position-1);
                }
            }
            if (position == 2) {

                if (checkSch){
                    ScheduleFragment scheduleFragment = new ScheduleFragment();
                    if (scheduleFragment.checkScheduleValidation()) {
                        Toast.makeText(CreateOrderActivity.this, "Validation okay", Toast.LENGTH_SHORT).show();
                    }else {
                        Toast.makeText(CreateOrderActivity.this, "Please check S validation", Toast.LENGTH_SHORT).show();
                        pagerCreateOrder.setCurrentItem(position-1);
                    }

                }else {

                    Toast.makeText(CreateOrderActivity.this, "Please check validation", Toast.LENGTH_SHORT).show();
                    pagerCreateOrder.setCurrentItem(position-2);
                }


            }


        }

//在checkScheduleValidation类中检查ScheduleFragment ()。返回空异常

*波洛甲壳脱核片段*

    public boolean checkServiceValidation(){


    return true;
}

我上传这张照片

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I used this Reference

Answer 1

我找到了解决办法。我在一个取景器里装了三个碎片。在第二个片段中，有一个编辑文本。在单击“下一步”按钮时，有一个检查电子邮件的验证。在验证的基础上，加载下一个片段。所有的碎片都是单例加载的。由于碎片的多个实例，可能导致了空指针异常。

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private SectionsPagerAdapter mSectionsPagerAdapter;
private FragmentTwo fragmentTwo;

private ViewPager mViewPager;
Button back, next;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    back = findViewById(R.id.back);
    next = findViewById(R.id.next);
    next.setOnClickListener(this);
    back.setOnClickListener(this);

    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    mViewPager = (ViewPager) findViewById(R.id.vp_viewpager);
    mViewPager.setAdapter(mSectionsPagerAdapter);
    mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int i, float v, int i1) {

        }

        @Override
        public void onPageSelected(int i) {
            if (i==2){
                if (!fragmentTwo.checkEditText()) {
                    Toast.makeText(getApplicationContext(),"False",Toast.LENGTH_LONG).show();
                    mViewPager.setCurrentItem(i-1);
                    return;
                }
            }


        }

        @Override
        public void onPageScrollStateChanged(int i) {

        }
    });


}

private void changeViewPagerPosition(int position) {
    int totalCount = mViewPager.getAdapter().getCount();
    if (position < 0 || position >= totalCount) {
        return;
    }
    mViewPager.setCurrentItem(position);
}

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

@Override
public void onClick(View view) {
    int currentViewpagerPosition = mViewPager.getCurrentItem();

    switch (view.getId()) {
        case R.id.back:
            changeViewPagerPosition(currentViewpagerPosition - 1);
            break;
        case R.id.next:
            if (currentViewpagerPosition==1){
                if (!fragmentTwo.checkEditText()) {
                    Toast.makeText(getApplicationContext(),"Falsee",Toast.LENGTH_LONG).show();
                    return;
                }

            }
            changeViewPagerPosition(currentViewpagerPosition + 1);
            break;
    }
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        switch (position) {

            case 0:
                return FragmentOne.newInstance(position);
            case 1:
                return fragmentTwo=FragmentTwo.getInstance();
            case 2:
                return FragmentThree.newInstance(position);
            default:
                return FragmentThree.newInstance(position);

        }

    }

    @Override
    public int getCount() {
        return 3;
    }
}

}

片段2

public  class FragmentTwo extends Fragment  {

EditText email;
private static FragmentTwo fragment=null;


public FragmentTwo() {
}

public static FragmentTwo getInstance() {
    if (fragment == null){
        fragment = new FragmentTwo();
    }
    return fragment;
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_two, container, false);
   return rootView;
}

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);


    email = getView().findViewById(R.id.editText);

}


public boolean emailValidator()
{
    Pattern pattern;
    Matcher matcher;
    final String EMAIL_PATTERN = "^[_A-Za-z0-" +
            "9-]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";
    pattern = Pattern.compile(EMAIL_PATTERN);
    matcher = pattern.matcher(email.getText().toString());
    return matcher.matches();
}


public Boolean checkEditText(){
    if (emailValidator()){
        return true;
    }
    return false;
}

}