Android 应用程序返回“错误：尝试调用虚拟方法 'java.lang.Object android.content.Context.getSystemService(java.lang.String)”

Question

I know there are similar questions like mine, but after 30 mins of research, I just can't figure it out.

Here is my error:

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.erikb.vinliste, PID: 12950
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.erikb.vinliste/com.example.erikb.vinliste.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2957)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032)
    at android.app.ActivityThread.-wrap11(Unknown Source:0)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
    at android.os.Handler.dispatchMessage(Handler.java:105)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6944)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
    at android.app.Dialog.<init>(Dialog.java:209)
    at android.app.AlertDialog.<init>(AlertDialog.java:201)
    at android.app.AlertDialog.<init>(AlertDialog.java:197)
    at dmax.dialog.SpotsDialog.<init>(SpotsDialog.java:79)
    at dmax.dialog.SpotsDialog.<init>(SpotsDialog.java:18)
    at dmax.dialog.SpotsDialog$Builder.build(SpotsDialog.java:62)
    at com.example.erikb.vinliste.MainActivity.onCreate(MainActivity.kt:43)
    at android.app.Activity.performCreate(Activity.java:7183)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1220)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2910)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032) 
    at android.app.ActivityThread.-wrap11(Unknown Source:0) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696) 
    at android.os.Handler.dispatchMessage(Handler.java:105) 
    at android.os.Looper.loop(Looper.java:164) 
    at android.app.ActivityThread.main(ActivityThread.java:6944) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374) 

And here is my Kotlin mainActivity file:

Imports:

import android.app.AlertDialog
import android.content.Intent
import android.content.pm.ActivityInfo
import android.graphics.Bitmap
import android.net.Uri
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.text.InputFilter
import android.widget.Toast
import com.example.erikb.vinliste.Helper.RectOverlay
import com.google.firebase.ml.vision.FirebaseVision
import com.google.firebase.ml.vision.barcode.FirebaseVisionBarcode
import com.google.firebase.ml.vision.common.FirebaseVisionImage
import com.wonderkiln.camerakit.*
import dmax.dialog.SpotsDialog
import kotlinx.android.synthetic.main.activity_main.*
import java.lang.StringBuilder
import com.google.firebase.ml.vision.barcode.FirebaseVisionBarcodeDetectorOptions 

And the rest:

class MainActivity : AppCompatActivity() {

    private lateinit var waiting_dialog:AlertDialog


    override fun onResume() {
        super.onResume()
        camera_view.start()
    }

    override fun onPause() {
        super.onPause()
        camera_view.stop()
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        requestedOrientation = (ActivityInfo.SCREEN_ORIENTATION_PORTRAIT)

        waiting_dialog = SpotsDialog.Builder().setMessage("Please wait").setCancelable(false).build()

        btn_detect.setOnClickListener {
            camera_view.start()
            camera_view.captureImage()
            graphic_overlay.clear()
        }

        camera_view.addCameraKitListener(object:CameraKitEventListener{
            override fun onVideo(p0: CameraKitVideo?) {

            }

            override fun onEvent(p0: CameraKitEvent?) {

            }

            override fun onImage(p0: CameraKitImage?) {
                waiting_dialog.show()

                var bitmap:Bitmap = p0!!.bitmap
                bitmap = Bitmap.createScaledBitmap(bitmap,camera_view.width,camera_view.height,false)
                camera_view.stop()

                runDetector(bitmap)
            }

            override fun onError(p0: CameraKitError?) {

            }

        })
    }

    private fun runDetector(bitmap: Bitmap?) {
        val image = FirebaseVisionImage.fromBitmap(bitmap!!)
        val options = FirebaseVisionBarcodeDetectorOptions.Builder()
            .setBarcodeFormats(
                FirebaseVisionBarcode.FORMAT_QR_CODE,
                FirebaseVisionBarcode.FORMAT_CODABAR
            )
            .build()
        val barcodeDetector = FirebaseVision.getInstance().getVisionBarcodeDetector(options)

        barcodeDetector.detectInImage(image)
            .addOnSuccessListener { result-> processResult(result) }
            .addOnFailureListener{ e-> Toast.makeText(this,e.message,Toast.LENGTH_SHORT).show()}
    }

    private fun processResult(result: List<FirebaseVisionBarcode>) {
        for(item in result) {
            var bounds = item.boundingBox
            var raw_value = item.rawValue
            var value_type = item.valueType

            //Draw rectangle
            val rect = RectOverlay(graphic_overlay,bounds)
            graphic_overlay.add(rect)

            //Show info
            when(value_type)
            {
                FirebaseVisionBarcode.TYPE_TEXT -> {
                    val alertDialog = AlertDialog.Builder(this)
                    alertDialog.setMessage(raw_value)
                    alertDialog.setPositiveButton("OK",{dialog, which -> dialog.dismiss()})
                    val dialog = alertDialog.create()
                    dialog.show()
                }
                FirebaseVisionBarcode.TYPE_URL -> {
                    val intent = Intent(Intent.ACTION_VIEW, Uri.parse(raw_value))
                    startActivity(intent)
                }

                FirebaseVisionBarcode.TYPE_CONTACT_INFO -> {

                    val name = item.contactInfo!!.name!!.formattedName
                    val address = item.contactInfo!!.addresses[0].addressLines[0]
                    val email = item.contactInfo!!.emails[0].address

                    val info = StringBuilder("Name: ").append(name).append("\n")
                        .append("Address: ").append(address).append("\n")
                        .append("Emal: ").append(email).toString()

                    val alertDialog = AlertDialog.Builder(this)
                    alertDialog.setMessage(info)
                    alertDialog.setPositiveButton("OK",{dialog, which -> dialog.dismiss()})
                    val dialog = alertDialog.create()
                    dialog.show()
                }
            }
        }

        waiting_dialog.dismiss()
    }
}

Spotsdialog

/* AUTO-GENERATED FILE.  DO NOT MODIFY.
 *
 * This class was automatically generated by the
 * gradle plugin from the resource data it found. It
 * should not be modified by hand.
 */
package dmax.dialog;

public final class R {
    private R() {}

    public static final class attr {
        private attr() {}

        public static final int DialogSpotColor = 0x7f020000;
        public static final int DialogSpotCount = 0x7f020001;
        public static final int DialogTitleAppearance = 0x7f020002;
        public static final int DialogTitleText = 0x7f020003;
    }
    public static final class color {
        private color() {}

        public static final int spots_dialog_color = 0x7f04005b;
    }
    public static final class dimen {
        private dimen() {}

        public static final int progress_margin = 0x7f05006a;
        public static final int progress_width = 0x7f05006b;
        public static final int spot_size = 0x7f05006c;
        public static final int title_margin = 0x7f05006d;
        public static final int title_padding = 0x7f05006e;
    }
    public static final class drawable {
        private drawable() {}

        public static final int dmax_spots_spot = 0x7f060068;
    }
    public static final class id {
        private id() {}

        public static final int dmax_spots_progress = 0x7f07003f;
        public static final int dmax_spots_title = 0x7f070040;
    }
    public static final class layout {
        private layout() {}

        public static final int dmax_spots_dialog = 0x7f09001d;
    }
    public static final class style {
        private style() {}

        public static final int SpotsDialogDefault = 0x7f0c00bc;
    }
    public static final class styleable {
        private styleable() {}

        public static final int[] Dialog = { 0x7f020000, 0x7f020001, 0x7f020002, 0x7f020003 };
        public static final int Dialog_DialogSpotColor = 0;
        public static final int Dialog_DialogSpotCount = 1;
        public static final int Dialog_DialogTitleAppearance = 2;
        public static final int Dialog_DialogTitleText = 3;
    }
}

Answer 1

I had to pull up the library for you Dialog builder. It looks like you're not setting the context when you build the SpotsDialog . Make sure in your SpotsDialog.Builder you add a context. Make sure you aren't missing anything else too, example from the library documentation:

val dialog: AlertDialog = SpotsDialog.Builder()
    .setContext(this)
    .setMessage(R.string.custom_title)
    .setCancelable(false)
    .build()

Check the library reference here for more: https://github.com/d-max/spots-dialog