在点击“add_product”时加载片段时出现空指针异常选项形成我的菜单选项。这里我的菜单选项在我的onoptionsitemselected内 [英] Null pointer exception while loading fragment while clicking on "add_product" option form my menu options . Here my menu options are inside my onoptionsitemselected

问题描述

public class ProductListActivity extends NavigationDrawerActivity
{

    private final String TAG = ProductListActivity.class.getSimpleName();
    private SectionsPagerAdapter mSectionsPagerAdapter;
    private ViewPager mViewPager;
    private ImageLoader imageLoader;
    private int lastTop = 0;
    private ProgressDialog mProgressDialog;
    private ArrayList<String> tabContent;
    private Context context;
    private CharSequence[] mMerchantCategoryName;
    private ArrayList<MasterCategory> categoriesList;
    private MasterCategory category;

    private ArrayList<Product> mMerchantProducts;

    private ArrayList<MasterCategory> mMerchantCategories;
    private HashMap<Integer, ArrayList<MasterCategory>> mMerchantSubCategories;
    private HashMap<Integer, ArrayList<MasterCategory>> mMerchantSubSubCategories;
    private HashMap<Integer, ArrayList<MasterCategory>> mMerchantSuperSubCategories;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        isViewPagerPresent = true;

        isViewPagerWithParalexPresent = true;
       super.onCreate(savedInstanceState);
        getWindow().setWindowAnimations(0);
       // setToolbarTitle("My Products");
        if (!EventBus.getDefault().isRegistered(this))
            EventBus.getDefault().register(this);
        context = this;
        initialiseUI();
        getMasterCategory();
    }

    public void initialiseUI()
    {
        imageLoader = Global.getInstance().getImageLoader();
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
        mViewPager = (ViewPager) findViewById(R.id.pager);
        //showSubCategoryTabs();
    }

    private void getMasterCategoryFromServer()
    {
        if(null == AmodaMerchantUser.getInstance().getMerchantCategories())
        {
            MerchantCategoryRequest merchantCategoryRequest = new MerchantCategoryRequest();
            ArrayList<Category> categories = AmodaMerchantUser.getInstance().getMerchantProfile().getVendorCategoryList();
            if (null != categories)
            {
                ArrayList<String> categoryIds = new ArrayList<>();
                for (int i = 0; i < categories.size(); i++)
                {
                    categoryIds.add("" + categories.get(i).getId());
                }

                merchantCategoryRequest.setCategoryIds(TextUtils.join(", ", categoryIds));
                merchantCategoryRequest.setMerchantId(AmodaMerchantUser.getInstance().getMerchantProfile().getMerchantId());
                if(null == mProgressDialog)
                    mProgressDialog = UIHelper.showProgressDialog(this, "One moment Please...", false, true);
                new WebServicesManager().getMerchantCategoryList(merchantCategoryRequest);
            }
        }
    }

    private void getMasterCategory()
    {
        /*mProgressDialog = UIHelper.showProgressDialog(this, "Please Wait...", false, true);
        MerchantCategoryRequest merchantCategoryRequest = new MerchantCategoryRequest();
        ArrayList<Category> categories = AmodaMerchantUser.getInstance().getMerchantProfile().getVendorCategoryList();
        ArrayList<String> categoryIds = new ArrayList<>();
        for (int i = 0; i < categories.size(); i++) {
            categoryIds.add("" + categories.get(i).getId());
        }

        merchantCategoryRequest.setCategoryIds(TextUtils.join(", ", categoryIds));
        merchantCategoryRequest.setMerchantId(AmodaMerchantUser.getInstance().getMerchantProfile().getMerchantId());
        new WebServicesManager().getMerchantCategoryList(merchantCategoryRequest);*/
        //mMerchantCategories         = AmodaMerchantUser.getInstance().getMerchantCategories();
        mMerchantSubCategories      = AmodaMerchantUser.getInstance().getMerchantSubCategories();
        mMerchantSubSubCategories   = AmodaMerchantUser.getInstance().getMerchantSubSubCategories();
        mMerchantSuperSubCategories = AmodaMerchantUser.getInstance().getMerchantSuperSubCategories();
        categoriesList = AmodaMerchantUser.getInstance().getMerchantCategories();

        if(null == categoriesList)
        {
            /*UIHelper.showOneButtonAlert(this, "Alert", "Your Profile expired. Please try again.", "OK", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    onBackPressed();
                }
            }, false);*/
            getMerchantProfile(PreferencesManager.getMerchantId());
        }
        else
        {
            mMerchantCategories = categoriesList;
            category = categoriesList.get(0);
            createCategoryHashTable();
            showSubCategoryTabs();
        }

    }

    private void getMerchantProfile(int merchantID)
    {
        mProgressDialog = UIHelper.showProgressDialog(this, "Profile expired, synchronising with server", false, true);
        new WebServicesManager().getMerchantProfile(new RequestManager().getMerchantProfileRequest(merchantID));
    }

    public void onEvent(MerchantProfileResponse merchantProfileResponse)
    {
        if (merchantProfileResponse != null && merchantProfileResponse.getStatusCode() == Constants.Merchant.HttpResponse.SUCCESS)
        {
            removePreviousProfile();
            DatabaseManager.MerchantProfileManager merchantProfileManager = new DatabaseManager().new MerchantProfileManager(this);
            merchantProfileManager.insertMerchantInDB(merchantProfileResponse);
            AmodaMerchantUser.getInstance().setMerchantProfile(merchantProfileResponse);
            PreferencesManager.setMerchantId(merchantProfileResponse.getMerchantId());
            getMasterCategoryFromServer();
        }
        else
        {
            UIHelper.stopProgressDialog(mProgressDialog);
            logoutUser();
        }
    }

    public void onEvent(MerchantCategoryResponse merchantCategoryResponse)
    {
        UIHelper.stopProgressDialog(mProgressDialog);
        if (Constants.Merchant.HttpResponse.SUCCESS == merchantCategoryResponse.getStatusCode())
        {
            AmodaMerchantUser.getInstance().createCategoryHashTable(merchantCategoryResponse.getCategoriesList());
            mMerchantSubCategories      = AmodaMerchantUser.getInstance().getMerchantSubCategories();
            mMerchantSubSubCategories   = AmodaMerchantUser.getInstance().getMerchantSubSubCategories();
            mMerchantSuperSubCategories = AmodaMerchantUser.getInstance().getMerchantSuperSubCategories();
            categoriesList = AmodaMerchantUser.getInstance().getMerchantCategories();
            mMerchantCategories = categoriesList;
            category = categoriesList.get(0);
            createCategoryHashTable();
            showSubCategoryTabs();
        }
        else
        {
            logoutUser();
        }
    }

    private void logoutUser()
    {
        Toast.makeText(this, "Can not synchronise with server, please login again.", Toast.LENGTH_SHORT).show();
        new WebServicesManager().merchantLogout(new RequestManager().getMerchantLogoutRequest(PreferencesManager.getMerchantId()));
        clearUserDataOnLogout();
        Intent intent = new Intent(this, BaseFragmentActivity.class);
        intent.putExtra("toolbarTitle", Constants.Merchant.ToolbarTitle.LOGIN);
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
        intent.putExtra("FragmentClassName", LoginFragment.class.getName());
        intent.putExtra("isLogin", true);
        startActivity(intent);
        finish();
    }

    private void removePreviousProfile()
    {
        DatabaseManager.MerchantProfileManager merchantProfileManager = new DatabaseManager().new MerchantProfileManager(this);
        Merchant merchantProfiles;
        long retVal = -1;
        do
        {
            merchantProfiles = merchantProfileManager.getMerchantProfile();
            if(null!= merchantProfiles)
                retVal = merchantProfileManager.deleteMerchantById(merchantProfiles);
        }while(null != merchantProfiles && retVal > 0);
    }

    /*public void onEvent(MerchantCategoryResponse merchantCategoryResponse) {
        UIHelper.stopProgressDialog(mProgressDialog);
        if (Constants.Merchant.HttpResponse.SUCCESS == merchantCategoryResponse.getStatusCode()) {
            categoriesList = merchantCategoryResponse.getCategoriesList();
            mMerchantCategories =  categoriesList;
            category = categoriesList.get(0);
            createCategoryHashTable();
            showSubCategoryTabs();
        } else {
           UIHelper.showOneButtonAlert(this, "Alert", "Merchant category details not found", "OK", null);
        }
    }*/

    private void showSubCategoryTabs()
    {
        setToolbarTitle(category != null ? category.getName() : "");
        try
        {
            mPromotionalImage.setDefaultImageResId(R.drawable.nodeals_img);
            mPromotionalImage.setImageUrl(category.getImageUrl(), imageLoader);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }

        tabContent = new ArrayList<String>();

        for (MasterCategory subCategories : category.getCategories()) {
            /*Check if the sub-sub category has super-sub category or not.*/
            if (null != subCategories.getCategories())
                tabContent.add(subCategories.getName());
        }

        mViewPager.setAdapter(mSectionsPagerAdapter);
        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE);
        tabLayout.setupWithViewPager(mViewPager);

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

            }

            @Override
            public void onPageSelected(int position) 
           {
                // callCategory.get(position).sendCategoryResponse();
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
    }

    public class SectionsPagerAdapter extends FragmentStatePagerAdapter
    {
        public SectionsPagerAdapter(FragmentManager fm)
        {
            super(fm);
        }

        @Override
        public Fragment getItem(int position)
        {
            MasterCategory subCategories = category.getCategories().get(position);
            if (subCategories.isHasChildCategory())
            {
                SubCategoryFragment subCategoryFragment = new SubCategoryFragment();
                Bundle bundle = new Bundle();
                bundle.putSerializable("iconImageURL", category.getIconImageUrl());
                bundle.putSerializable("data", category.getCategories().get(position));
                subCategoryFragment.setArguments(bundle);
                return subCategoryFragment;
            }
            else
            {
                SubCategoryProductsFragment subCategoryProductsFragment = new SubCategoryProductsFragment();
                Bundle bundle = new Bundle();
                bundle.putInt("categoryId", subCategories.getCategoryId());
                bundle.putString("categoryName", subCategories.getName());
                bundle.putBoolean("isSubCatProducts", true);
                subCategoryProductsFragment.setArguments(bundle);
                return subCategoryProductsFragment;
            }
        }

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

        @Override
        public CharSequence getPageTitle(int position) {
            Locale l = Locale.getDefault();
            return tabContent.get(position);
        }
    }

    @Override
    public void onResume()
    {
        if (!EventBus.getDefault().isRegistered(this))
            EventBus.getDefault().register(this);
        super.onResume();
    }

    @Override
    protected void onPause() {
        super.onPause();
    }

    @Override
    public void onStop()
    {
        super.onStop();
        //*Unregister event bus when the app goes in background*//*
        if (EventBus.getDefault().isRegistered(this))
            EventBus.getDefault().unregister(this);
    }


    @Override
    public void onDestroy()
    {
        super.onDestroy();
        if (EventBus.getDefault().isRegistered(this))
            EventBus.getDefault().unregister(this);
    }

    public void onError(VolleyError volleyError) {
        UIHelper.stopProgressDialog(mProgressDialog);
        Functions.Application.VolleyErrorCheck(this, volleyError);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        getMenuInflater().inflate(R.menu.menu_category_change, menu);
        MenuItem categoryMenuItem = menu.findItem(R.id.category);
        boolean visible;
        if (null != categoriesList && categoriesList.size() > 1)
        {
            visible = true;
        }
        else
        {
            visible = false;
        }
        categoryMenuItem.setVisible(visible);
        return true;
    }

    public boolean onOptionsItemSelected(MenuItem item)
    {
        switch (item.getItemId())
        {
            case R.id.category:
                displayCategories();
                break;

            case R.id.add_product:
                Intent addProductIntent = new Intent(this, BaseFragmentActivity.class);
                addProductIntent.putExtra("Categories", mMerchantCategories);
                addProductIntent.putExtra("SubCategories", mMerchantSubCategories);
                addProductIntent.putExtra("SubSubCategories", mMerchantSubSubCategories);
                addProductIntent.putExtra("SuperSubCategories", mMerchantSuperSubCategories);
                addProductIntent.putExtra("FragmentClassName", AddProductFragment.class.getName());
                startActivity(addProductIntent);
                break;

              /*  CustomDialogAddProductOption addproduct=new CustomDialogAddProductOption(context,mMerchantCategories,mMerchantSubCategories,mMerchantSubSubCategories,mMerchantSuperSubCategories);
                addproduct.show();
*/
            case R.id.changeproductprice:
                changeproductprice();
                break;

            default:
                return super.onOptionsItemSelected(item);
        }
        return true;
    }

    public void displayCategories()
    {

        getMasterCategoryFromServer();

        if (!categoriesList.isEmpty())
        {

            mMerchantCategoryName = new String[categoriesList.size()];
            for (int i = 0; i < categoriesList.size(); i++)
            {
                mMerchantCategoryName[i] = categoriesList.get(i).getName();
            }
            AlertDialog.Builder builder = new AlertDialog.Builder(context);

            builder.setTitle("Select Category");

            builder.setItems(mMerchantCategoryName, new DialogInterface.OnClickListener()
            {
                public void onClick(DialogInterface dialog, int item)
                {

                   category = categoriesList.get(item);
                    showSubCategoryTabs();
                }
            });

            builder.setNegativeButton("Cancel", null);
            AlertDialog alert = builder.create();
            alert.show();
        }
    }

    private void createCategoryHashTable()
    {
        mMerchantSubCategories = new HashMap<>();
        mMerchantSubSubCategories = new HashMap<>();
        mMerchantSuperSubCategories = new HashMap<>();
        if (null != mMerchantCategories)
        {
            /*Get merchant's sub-category from database*/
            for (int i = 0; i < mMerchantCategories.size(); i++)
            {
                try
                {
                    mMerchantSubCategories.put(mMerchantCategories.get(i).getCategoryId(), mMerchantCategories.get(i).getCategories());
                }
                catch (Exception e)
                {
                    e.printStackTrace();
                }
            }
            /*Get merchant's sub-sub-category from database*/
            for (int i = 0; i < mMerchantSubCategories.size(); i++) {
                for (int j = 0; j < mMerchantSubCategories.get(mMerchantCategories.get(i).getCategoryId()).size(); j++) {
                    try {
                        mMerchantSubSubCategories.put(mMerchantSubCategories.get(mMerchantCategories.get(i).getCategoryId()).get(j).getCategoryId(),
                                mMerchantSubCategories.get(mMerchantCategories.get(i).getCategoryId()).get(j).getCategories());
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }


            }
            /*Get merchant's super-sub-category from database*/
            for (int subCategoryId = 0; subCategoryId < mMerchantSubCategories.size(); subCategoryId++) {
                for (int i = 0; i < mMerchantCategories.get(subCategoryId).getCategories().size(); i++) {
                    for (int j = 0; j < mMerchantSubSubCategories.get(mMerchantCategories.get(subCategoryId).getCategories().get(i).getCategoryId()).size(); j++) {
                        try {
                            mMerchantSuperSubCategories.put(mMerchantSubSubCategories.get(mMerchantCategories.get(subCategoryId).getCategories().get(i).getCategoryId()).get(j).getCategoryId(),
                                    mMerchantSubSubCategories.get(mMerchantCategories.get(subCategoryId).getCategories().get(i).getCategoryId()).get(j).getCategories());
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }
    }

    public void changeproductprice()
    {
        new WebServicesManager().UpdateProductPrice(new RequestManager().getUpdateProductPriceRequest(AmodaMerchantUser.getInstance().getMerchantProfile().getMerchantId()));
        Toast.makeText(context,"Email sent successfully",Toast.LENGTH_LONG).show();
    }
}

我的尝试：



我尝试解决空指针异常。 I created a dialog and then gave it two options of which if user clicks on one of the options then the fragment will load . Inside the fragment instead of assigning direct values to the fragment as shown above,I fetched the data directly from another java class.

What I have tried:

I tried solving the null pointer exception . I created a dialog and then gave it two options of which if user clicks on one of the options then the fragment will load . Inside the fragment instead of assigning direct values to the fragment as shown above,I fetched the data directly from another java class.

推荐答案

This is one of the most common problems we get asked, and it’s also the one we are least equipped to answer, but you are most equipped to answer yourself.



Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.

It’s a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen.如果你进入口袋并发现那里没有笔，你就不能在一张纸上签名 - 如果你尝试的话，你会得到非常有趣的外观！空口袋给你一个空值（这里没有笔！）所以你不能做任何你检索笔通常做的事情。它为什么空？ That’s the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night.



We can’t tell, because we weren’t there, and even more importantly, we can’t even see your shirt, much less what is in the pocket!



Back to computers, and you have done the same thing, somehow - and we can’t see your code, much less run it and find out what contains null when it shouldn’t.

But you can - and your IDE of choice will help you here. Run your program in the debugger and when it fails, it will show you the line it found the problem on.然后，您可以开始查看它的各个部分，以查看哪个值为null，并开始回顾代码以找出原因。因此，在包含错误行的方法的开头放置一个断点，然后从头再次运行程序。这一次，VS会在错误发生前停止，让你通过查看代码来查看你的价值来检查发生了什么。



但我们做不到那 - 我们没有您的代码，如果我们拥有它，我们不知道如何使用它，我们没有您的数据。所以试试吧 - 看看你能找到多少信息！

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and your IDE of choice will help you here. Run your program in the debugger and when it fails, it will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!

这篇关于在点击“add_product”时加载片段时出现空指针异常选项形成我的菜单选项。这里我的菜单选项在我的onoptionsitemselected内的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！