CODEWITHSUNDEEP
androidandroid-studiolistviewlistadaptercustom-lists
user10366889
user10366889

Reputation:

Android Studio null exception error on a ListView with custom ListAdapter

[Edited] This is the mainScreen activity xml as requested by some of you

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:design="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#F6F6F6">


    <TextView
        android:id="@+id/textView8"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="4dp"
        android:fontFamily="@font/montserrat"
        android:text="Pocket Budget"
        android:textColor="#77dd77"
        android:textSize="26dp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView9"
        android:layout_width="138dp"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:fontFamily="@font/montserrat"
        android:gravity="center"
        android:text="January"
        android:textColor="#443c3c"
        android:textSize="16dp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="@+id/textView8"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/textView8"
        app:layout_constraintTop_toTopOf="@+id/textView8" />

    <View
        android:id="@+id/view5"
        android:layout_width="match_parent"
        android:layout_height="56dp"
        android:layout_marginTop="7dp"
        android:background="#FFF"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView8" />

    <View
        android:id="@+id/view2"
        android:layout_width="116dp"
        android:layout_height="50dp"
        android:layout_marginBottom="3dp"
        android:layout_marginEnd="3dp"
        android:layout_marginTop="3dp"
        android:background="#77dd77"
        app:layout_constraintBottom_toBottomOf="@+id/view5"
        app:layout_constraintEnd_toEndOf="@+id/view5"
        app:layout_constraintTop_toTopOf="@+id/view5" />

    <View
        android:id="@+id/view3"
        android:layout_width="116dp"
        android:layout_height="50dp"
        android:layout_marginBottom="3dp"
        android:layout_marginStart="3dp"
        android:layout_marginTop="3dp"
        android:background="#779ecb"
        app:layout_constraintBottom_toBottomOf="@+id/view5"
        app:layout_constraintStart_toStartOf="@+id/view5"
        app:layout_constraintTop_toTopOf="@+id/view5" />

    <View
        android:id="@+id/view4"
        android:layout_width="116dp"
        android:layout_height="50dp"
        android:layout_marginBottom="3dp"
        android:layout_marginEnd="3dp"
        android:layout_marginStart="3dp"
        android:layout_marginTop="3dp"
        android:background="#ff6961"
        app:layout_constraintBottom_toBottomOf="@+id/view5"
        app:layout_constraintEnd_toStartOf="@+id/view2"
        app:layout_constraintStart_toEndOf="@+id/view3"
        app:layout_constraintTop_toTopOf="@+id/view5" />

    <TextView
        android:id="@+id/textView12"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="2dp"
        android:fontFamily="@font/montserrat"
        android:text="Balance"
        android:textColor="#FFF"
        android:textSize="9.5dp"
        app:layout_constraintBaseline_toBaselineOf="@+id/textView2"
        app:layout_constraintStart_toStartOf="@+id/view2" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="2dp"
        android:fontFamily="@font/montserrat"
        android:text="Expense"
        android:textColor="#FFF"
        android:textSize="9.5dp"
        design:layout_constraintBaseline_toBaselineOf="@+id/textView"
        design:layout_constraintStart_toStartOf="@+id/view4" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="2dp"
        android:fontFamily="@font/montserrat"
        android:text="Income"
        android:textColor="#FFF"
        android:textSize="9.5dp"
        design:layout_constraintStart_toStartOf="@+id/view3"
        design:layout_constraintTop_toTopOf="@+id/view3" />

    <TextView
        android:id="@+id/textView4"
        android:layout_width="116dp"
        android:layout_height="25dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:autoSizeTextType="uniform"
        android:fontFamily="@font/montserrat"
        android:gravity="center"
        android:text="₱ 0"
        android:textColor="#FFF"
        android:textSize="20dp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="@+id/textView6"
        app:layout_constraintEnd_toEndOf="@+id/view3"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="@+id/view3"
        app:layout_constraintTop_toTopOf="@+id/textView6"
        app:layout_constraintVertical_bias="1.0" />

    <TextView
        android:id="@+id/textView6"
        android:layout_width="116dp"
        android:layout_height="25dp"
        android:layout_marginBottom="8dp"
        android:layout_marginStart="8dp"
        android:autoSizeTextType="uniform"
        android:fontFamily="@font/montserrat"
        android:gravity="center"
        android:text="₱ 0"
        android:textColor="#FFF"
        android:textSize="20dp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="@+id/view4"
        app:layout_constraintEnd_toEndOf="@+id/view4"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="@+id/view4"
        app:layout_constraintTop_toBottomOf="@+id/textView2"
        app:layout_constraintVertical_bias="0.0" />

    <TextView
        android:id="@+id/textView11"
        android:layout_width="116dp"
        android:layout_height="25dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="12dp"
        android:layout_marginTop="8dp"
        android:autoSizeTextType="uniform"
        android:fontFamily="@font/montserrat"
        android:gravity="center"
        android:text="₱ 0"
        android:textColor="#FFF"
        android:textSize="20dp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="@+id/textView6"
        app:layout_constraintEnd_toEndOf="@+id/view2"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="@+id/view2"
        app:layout_constraintTop_toTopOf="@+id/textView6" />

    <TextView
        android:id="@+id/textView5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="5dp"
        android:fontFamily="@font/montserrat"
        android:text="Transactions"
        android:textColor="#808080"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/view5" />

    <ListView
        android:id="@+id/transacList"
        android:layout_width="344dp"
        android:layout_height="438dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:background="#FFF"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView5"
        app:layout_constraintVertical_bias="0.0"></ListView>
</android.support.constraint.ConstraintLayout>

This is the code for my custom ListView I don't know what's wrong because I'm just a beginner in android development

package com.example.admin.test2;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

import org.w3c.dom.Text;

import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extends AppCompatActivity {

    ListView mListView;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        new Timer().schedule(new TimerTask(){
            @Override
            public void run(){
                startActivity(new Intent(MainActivity.this, ScreenOne.class));
            }
        }, 2500);

        mListView = (ListView) findViewById(R.id.transacList);

        CustomAdaptor cAdaptor = new CustomAdaptor();
        mListView.setAdapter(cAdaptor);

    }

    class CustomAdaptor extends BaseAdapter{

        @Override
        public int getCount() {
            return 0;
        }

        @Override
        public Object getItem(int position) {
            return null;
        }

        @Override
        public long getItemId(int position) {
            return 0;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            View view = getLayoutInflater().inflate(R.layout.customlist, null);

            ImageView mImageView = (ImageView) view.findViewById(R.id.imageView2);
            TextView mTextView = (TextView) view.findViewById(R.id.textView2);
            TextView mTextView2 = (TextView) view.findViewById(R.id.textView3);

            mImageView.setImageResource(R.drawable.car);
            mTextView.setText("Transportation");
            mTextView2.setText("₱ 100");


            return view;
        }
    }

}

And this is the code for my custom listview layout that will be implemented in my mainScreen for viewing the image icon with the label and amount

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">


    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="36dp"
        android:layout_height="36dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="19dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.015"
        app:srcCompat="@mipmap/ic_launcher" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="120dp"
        android:layout_height="25dp"
        android:layout_marginBottom="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:autoSizeTextType="uniform"
        android:text="Label"
        android:textSize="20dp"
        app:layout_constraintBottom_toBottomOf="@+id/imageView2"
        app:layout_constraintStart_toEndOf="@+id/imageView2"
        app:layout_constraintTop_toTopOf="@+id/imageView2"
        app:layout_constraintVertical_bias="1.0" />

    <TextView
        android:layout_width="147dp"
        android:layout_height="21dp"
        android:layout_marginEnd="18dp"
        android:layout_marginStart="8dp"
        android:autoSizeTextType="uniform"
        android:gravity="right"
        android:text="Amount"
        app:layout_constraintBottom_toBottomOf="@+id/textView3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toEndOf="@+id/textView3"
        app:layout_constraintTop_toTopOf="@+id/textView3"
        app:layout_constraintVertical_bias="1.0" />


</android.support.constraint.ConstraintLayout>

This is the error that I encountered.

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.admin.test2, PID: 9518
                  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.admin.test2/com.example.admin.test2.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' 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 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
                      at com.example.admin.test2.MainActivity.onCreate(MainActivity.java:37)
                      at android.app.Activity.performCreate(Activity.java:7174)
                      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) 

someone please help solving this problem the application when run is force closing and I don't know what is wrong.

Upvotes: 0

Views: 201

Answers (4)

Haroun Hajem
Haroun Hajem

Reputation: 5628

ListView is null, so you can't set it's adapter. Hence you get this error: 

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference

findViewById(R.id.transacList) returns null beacuse the ID is wrong or the casting is wrong or your custom listview is messed up. Can't judge that from the code you provided.

Upvotes: 0

Dr BigKitkat
Dr BigKitkat

Reputation: 423

You didn't initialize the list view, add this line before setting the adapter. mListView = findViewById(R.id.*your list view id*);

Upvotes: 0

Furkan Yurdakul
Furkan Yurdakul

Reputation: 3167

You don't have any listviews on your layout, hence you get this exception. Try adding something like this: 

<ListView
        android:id="@+id/transacList"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="19dp"
        android:layout_marginTop="8dp" />

Margins and paddings should be designed for your usage of the listview.

Upvotes: 0

WatchMyApps Lab
WatchMyApps Lab

Reputation: 121

It looks like your ListView "mListView" is not initialized yet, make sure your you are properly initializing it, will be helpful if you share your activity_main.xml code.

Upvotes: 0

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