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androidtimernumberpicker

Getting a null pointer exception on a number picker - Android

I am trying to do a simple "number picker" function that was custom made (not using the NumberPicker widget), by aligning 3 of them side by side. I got one to work just fine, but as soon as I added the other 2, then tried to change variable names (and adjusted it in the MainActivity), the program crashed with a NullPointer Exception. It is saying line 29 is the culprit (caused by) in the MainActivity.

I probably don't understand the MainActivity code very well, as it was code I borrowed. Why is it crashing? Thanks.

MainActivity.java

package com.azurespot.numbpicksample;

import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.app.Activity;

public class MainActivity extends Activity implements OnClickListener {
    Button btnUp, btnDown;
    TextView textViewUp, textViewMid, textViewBottom;

    int nStart = 0;
    int nEnd = 59;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btnUp = (Button) findViewById(R.id.buttonUp1|R.id.buttonUp2|R.id.buttonUp3);
        btnDown = (Button) findViewById(R.id.buttonDown1|R.id.buttonDown2|R.id.buttonDown3);

        // All the numbers
        textViewUp = (TextView) findViewById(R.id.plus1|R.id.plus2|R.id.plus3);
        textViewMid = (TextView) findViewById(R.id.mainNumber1|R.id.mainNumber2|R.id.mainNumber3);
        textViewBottom = (TextView) findViewById(R.id.minus1|R.id.minus2|R.id.minus3);

        textViewUp.setText("1"); // Line 29
        textViewMid.setText("0");
        textViewBottom.setText("59");

        btnUp.setOnClickListener(this);
        btnDown.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        String getString = String.valueOf(textViewMid.getText());
        int current = Integer.parseInt(getString);
        if (v == btnUp) {
            if (current < nEnd) {
                current++;
                textViewUp.setText(String.valueOf(current - 1));
                textViewMid.setText(String.valueOf(current));
                textViewBottom.setText(String.valueOf(current + 1));
            }

        }
        if (v == btnDown) {
            if (current > nStart) {
                current--;
                textViewUp.setText(String.valueOf(current - 1));
                textViewMid.setText(String.valueOf(current));
                textViewBottom.setText(String.valueOf(current + 1));
            }
        }
    }
}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="horizontal" >

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="left"
        android:orientation="vertical" >

        <Button
            android:id="@+id/buttonUp1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:background="@drawable/up_btn" />

        <TextView
            android:id="@+id/plus1"
            android:layout_width="43dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:text="plus"
            android:textColor="#cc8400"
            android:textSize="16sp" />

        <View
            android:id="@+id/topBar1"
            android:layout_width="30dp"
            android:layout_height="1dp"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:layout_marginTop="10dp"
            android:background="#000000" />

        <TextView
            android:id="@+id/mainNumber1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:text="Main"
            android:textColor="#000000"
            android:textSize="30sp" />

        <View
            android:id="@+id/lowerBar1"
            android:layout_width="30dp"
            android:layout_height="1dp"
            android:layout_marginBottom="5dp"
            android:layout_gravity="center_horizontal"
            android:background="#000000" />

        <TextView
            android:id="@+id/minus1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:text="minus"
            android:textColor="#cc8400"
            android:textSize="16sp" />

        <Button
            android:id="@+id/buttonDown1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:background="@drawable/down_btn" />

    </LinearLayout>

<!-- start center numberpicker -->

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:orientation="vertical" >

        <Button
            android:id="@+id/buttonUp2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:background="@drawable/up_btn" />

        <TextView
            android:id="@+id/plus2"
            android:layout_width="43dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:text="plus"
            android:textColor="#cc8400"
            android:textSize="16sp" />

        <View
            android:id="@+id/topBar2"
            android:layout_width="30dp"
            android:layout_height="1dp"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:layout_marginTop="10dp"
            android:background="#000000" />

        <TextView
            android:id="@+id/mainNumber2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:text="Main"
            android:textColor="#000000"
            android:textSize="30sp" />

        <View
            android:id="@+id/lowerBar2"
            android:layout_width="30dp"
            android:layout_height="1dp"
            android:layout_marginBottom="5dp"
            android:layout_gravity="center_horizontal"
            android:background="#000000" />

        <TextView
            android:id="@+id/minus2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:text="minus"
            android:textColor="#cc8400"
            android:textSize="16sp" />

        <Button
            android:id="@+id/buttonDown2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:background="@drawable/down_btn" />

    </LinearLayout>

    <!-- start right numberpicker -->

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:orientation="vertical" >

        <Button
            android:id="@+id/buttonUp3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:background="@drawable/up_btn" />

        <TextView
            android:id="@+id/plus3"
            android:layout_width="43dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:text="plus"
            android:textColor="#cc8400"
            android:textSize="16sp" />

        <View
            android:id="@+id/topBar3"
            android:layout_width="30dp"
            android:layout_height="1dp"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:layout_marginTop="10dp"
            android:background="#000000" />

        <TextView
            android:id="@+id/mainNumber3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:text="Main"
            android:textColor="#000000"
            android:textSize="30sp" />

        <View
            android:id="@+id/lowerBar3"
            android:layout_width="30dp"
            android:layout_height="1dp"
            android:layout_marginBottom="5dp"
            android:layout_gravity="center_horizontal"
            android:background="#000000" />

        <TextView
            android:id="@+id/minus3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginBottom="5dp"
            android:text="minus"
            android:textColor="#cc8400"
            android:textSize="16sp" />

        <Button
            android:id="@+id/buttonDown3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:background="@drawable/down_btn" />

    </LinearLayout>

</LinearLayout>

LogCat

FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.azurespot.numbpicksample/com.azurespot.numbpicksample.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
            at android.app.ActivityThread.access$600(ActivityThread.java:141)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5041)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.azurespot.numbpicksample.MainActivity.onCreate(MainActivity.java:29)
            at android.app.Activity.performCreate(Activity.java:5104)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
            at android.app.ActivityThread.access$600(ActivityThread.java:141)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5041)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
Solution

  • You cant use | to separate layout variables while initialising..

    So replace this 

    btnUp = (Button) findViewById(R.id.buttonUp1|R.id.buttonUp2|R.id.buttonUp3);

    as

     btnUp = (Button) findViewById(R.id.buttonUp1);

    Similarly do it for others also..