android - Kotlin 内部类无法发起 Session 对象

Question

    import android.content.Context
import android.graphics.Color
import android.net.Uri
import android.support.design.widget.TabLayout
import android.support.v4.app.Fragment
import android.support.v4.app.FragmentManager
import android.support.v4.app.FragmentPagerAdapter
import android.support.v4.view.ViewPager
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.LayoutInflater
import android.widget.TextView
import android.widget.Toolbar
import java.util.ArrayList
import com.salesrep.auxxa.alliontechnologies.auxxasr.R.id.viewPager

import android.graphics.drawable.GradientDrawable
import android.support.v4.app.FragmentStatePagerAdapter
import android.support.v4.view.PagerAdapter
import android.util.Log
import com.salesrep.auxxa.alliontechnologies.auxxasr.utillities.Session
import org.json.JSONObject


class NewPaymentActivity : AppCompatActivity(),SummaryFragment.OnFragmentInteractionListener,ReceiptDetailsFragment.OnFragmentInteractionListener{

    internal lateinit var viewpageradapter: ViewPagerAdapter //Declare PagerAdapter

    private var tabLayout: TabLayout? = null
    var viewPager: ViewPager? = null
    var toolbar: Toolbar? = null
    var myPreference : Session? =null

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_new_payment)
        myPreference= Session(this)
        viewpageradapter= ViewPagerAdapter(supportFragmentManager)

        viewPager = findViewById(R.id.viewPager) as ViewPager
        setupViewPager(viewPager!!)

        tabLayout = findViewById(R.id.tab_layout) as TabLayout
        tabLayout!!.setupWithViewPager(viewPager)

//      tabLayout!!.setSelectedTabIndicatorColor(getResources().getColor(R.color.t));
        tabLayout!!.setSelectedTabIndicatorHeight(0)




        val headerView = (getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater)
                .inflate(R.layout.custom_tabs_for_payments, null, false)

        val receiptDetails = headerView.findViewById(R.id.tb_receipt_details) as TextView
        val paymentDetails = headerView.findViewById(R.id.tb_payment_details) as TextView
        val invoiceDetails = headerView.findViewById(R.id.tb_invoice_details) as TextView
        val summary = headerView.findViewById(R.id.tb_summary) as TextView

        receiptDetails.setTextColor(resources.getColor(R.color.white))
        val drawable = receiptDetails.getBackground() as GradientDrawable
        drawable.setColor(resources.getColor(R.color.received_payments))

        paymentDetails.setTextColor(resources.getColor(R.color.main))
        val drawablepaymentDetails = paymentDetails.getBackground() as GradientDrawable
        drawablepaymentDetails.setColor(resources.getColor(R.color.white))

        invoiceDetails.setTextColor(resources.getColor(R.color.main))
        val drawableinvoiceDetails = invoiceDetails.getBackground() as GradientDrawable
        drawableinvoiceDetails.setColor(resources.getColor(R.color.white))

        summary.setTextColor(resources.getColor(R.color.main))
        val summarydrawable = summary.getBackground() as GradientDrawable
        summarydrawable.setColor(resources.getColor(R.color.white))

        tabLayout!!.getTabAt(0)!!.setCustomView(receiptDetails)
        tabLayout!!.getTabAt(1)!!.setCustomView(paymentDetails)
        tabLayout!!.getTabAt(2)!!.setCustomView(invoiceDetails)
        tabLayout!!.getTabAt(3)!!.setCustomView(summary)



        tabLayout!!.addOnTabSelectedListener(object : TabLayout.OnTabSelectedListener {

            override fun onTabSelected(tab: TabLayout.Tab?) {

                if(tab!!.position==0)
                {
                    Log.e("tab","0")

                    receiptDetails.setTextColor(resources.getColor(R.color.white))
                    val drawable = receiptDetails.getBackground() as GradientDrawable
                    drawable.setColor(resources.getColor(R.color.received_payments))

                    paymentDetails.setTextColor(resources.getColor(R.color.main))
                    val drawablepaymentDetails = paymentDetails.getBackground() as GradientDrawable
                    drawablepaymentDetails.setColor(resources.getColor(R.color.white))

                    invoiceDetails.setTextColor(resources.getColor(R.color.main))
                    val drawableinvoiceDetails = invoiceDetails.getBackground() as GradientDrawable
                    drawableinvoiceDetails.setColor(resources.getColor(R.color.white))

                    summary.setTextColor(resources.getColor(R.color.main))
                    val summarydrawable = summary.getBackground() as GradientDrawable
                    summarydrawable.setColor(resources.getColor(R.color.white))
                }
                else if(tab!!.position==1 && myPreference!!.getReceiptStatus())
                {

                    Log.e("tab","1")
                    Log.e("stataus",myPreference!!.getReceiptStatus().toString())

                    paymentDetails.setTextColor(resources.getColor(R.color.white))
                    val drawable = paymentDetails.getBackground() as GradientDrawable
                    drawable.setColor(resources.getColor(R.color.received_payments))

                    receiptDetails.setTextColor(resources.getColor(R.color.main))
                    val drawablereceiptDetails= receiptDetails.getBackground() as GradientDrawable
                    drawablereceiptDetails.setColor(resources.getColor(R.color.white))

                    invoiceDetails.setTextColor(resources.getColor(R.color.main))
                    val drawableinvoiceDetails = invoiceDetails.getBackground() as GradientDrawable
                    drawableinvoiceDetails.setColor(resources.getColor(R.color.white))

                    summary.setTextColor(resources.getColor(R.color.main))
                    val summarydrawable = summary.getBackground() as GradientDrawable
                    summarydrawable.setColor(resources.getColor(R.color.white))


                }
                else if(tab!!.position==2)
                {
                    Log.e("tab","2")

                    invoiceDetails.setTextColor(resources.getColor(R.color.white))
                    val drawable = invoiceDetails.getBackground() as GradientDrawable
                    drawable.setColor(resources.getColor(R.color.received_payments))

                    receiptDetails.setTextColor(resources.getColor(R.color.main))
                    val drawablereceiptDetails= receiptDetails.getBackground() as GradientDrawable
                    drawablereceiptDetails.setColor(resources.getColor(R.color.white))

                    paymentDetails.setTextColor(resources.getColor(R.color.main))
                    val drawablepaymentDetails = paymentDetails.getBackground() as GradientDrawable
                    drawablepaymentDetails.setColor(resources.getColor(R.color.white))

                    summary.setTextColor(resources.getColor(R.color.main))
                    val summarydrawable = summary.getBackground() as GradientDrawable
                    summarydrawable.setColor(resources.getColor(R.color.white))


                }
                else if(tab!!.position==3)
                {
                    Log.e("tab","3")

                    summary.setTextColor(resources.getColor(R.color.white))
                    val drawable = summary.getBackground() as GradientDrawable
                    drawable.setColor(resources.getColor(R.color.received_payments))

                    receiptDetails.setTextColor(resources.getColor(R.color.main))
                    val drawablereceiptDetails = receiptDetails.getBackground() as GradientDrawable
                    drawablereceiptDetails.setColor(resources.getColor(R.color.white))

                    paymentDetails.setTextColor(resources.getColor(R.color.main))
                    val drawablepaymentDetails = paymentDetails.getBackground() as GradientDrawable
                    drawablepaymentDetails.setColor(resources.getColor(R.color.white))

                    invoiceDetails.setTextColor(resources.getColor(R.color.main))
                    val drawableinvoiceDetails = invoiceDetails.getBackground() as GradientDrawable
                    drawableinvoiceDetails.setColor(resources.getColor(R.color.white))
                }
                else {

                }

            }
            override fun onTabUnselected(tab:TabLayout.Tab?){
            }
            override fun onTabReselected(tab:TabLayout.Tab?) {
            }
        })


    }

    private fun setupViewPager(viewPager: ViewPager) {
        viewPager.setOffscreenPageLimit(-1);
        val adapter = ViewPagerAdapter(supportFragmentManager)
        viewPager.adapter = adapter



    }

   inner class ViewPagerAdapter(manager: FragmentManager) : FragmentPagerAdapter(manager) {



        override fun getItem(position: Int): Fragment? {
            var fragment: Fragment? = null

            if (position == 0 ) {
                Log.e("frag",position.toString())
                fragment = ReceiptDetailsFragment()
            } else if (position == 1 && myPreference!!.getReceiptStatus() ) {
                Log.e("frag",position.toString())
                fragment = PaymentDetailsFragment()
            } else if (position == 2) {
                Log.e("frag",position.toString())
                fragment = InvoiceDetailsFragment()
            } else if (position == 3) {
                Log.e("frag",position.toString())
                fragment = InvoiceDetailsFragment()
            }
            return fragment
        }

        override fun getPageTitle(position: Int): CharSequence {
            return when (position) {
                0 -> "Receipt Details"
                1 -> "Payment Details"
                2 -> "Invocie Details"
                3 -> "Summary"
                else -> throw IllegalArgumentException()
            }
        }

        override fun getCount(): Int {
            return 4
        }
    }

    override fun onFragmentInteraction(jsonObject: JSONObject) {
        //session intialization
        val myPreference = Session(this)
        myPreference.setJsonObject(jsonObject.toString())
        viewPager!!.setCurrentItem(1,true)


    }


    override fun onFragmentInteraction(uri: Uri) {

    }

}

private operator fun Int.invoke(i: Int) {

}

Above I have attched my NewPaymentActivity class.But issue is that I got one null pointer exception once I run this code.I need to use session values inside my inner class.But It seems session initialization pass null value. Inside inner class I used myPreference!!.getReceiptStatus() but myPreference value is null.Below I'll attch my log record also.

 Process: com.salesrep.auxxa.alliontechnologies.auxxasr, PID: 6082
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Class java.lang.Object.getClass()' on a null object reference

Answer 1

myPreference!!.getReceiptStatus()

避免使用“!!”，始终检查是否可为空，

myPreference?.let { it.getReceiptStatus() } 

这样使用，异常就解决了

override fun onFragmentInteraction(jsonObject: JSONObject) {
    //session intialization
    val myPreference = Session(this)
    myPreference.setJsonObject(jsonObject.toString())
    viewPager!!.setCurrentItem(1,true)


}

这里你正在分配 myPreference 的局部变量，我认为你可能需要更改或将其分配给全局变量只需从 - val myPreference = Session(this)

中删除 val