Android null pointer exception on view.getId()

Question

This code gives a null pointer exception in the onClick() method. I checked other posts but didn't get proper solutions. Please help. This is my first android project and so I can't solve it. Where is the error in this? This seems to be the way I have seen in other solutions

    public class MainActivity extends Activity implements OnClickListener{

        Button btn0,btn1,btn2,btn3,btn4,btn5,btn6,btn7,btn8,btn9,btnAdd,btnSub,btnDiv,btnMul,btnDot,btnSign,btnAns,btnCE,btnC,btnDel;
        EditText et;
        char last;
        double num,num1,num2;
        boolean signFlag,numFlag;

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

            //Initializing variables
            btn0=(Button) findViewById(R.id.btn0);
            btn1=(Button) findViewById(R.id.btn1);
            btn2=(Button) findViewById(R.id.btn2);
            btn3=(Button) findViewById(R.id.btn3);
            btn4=(Button) findViewById(R.id.btn4);
            btn5=(Button) findViewById(R.id.btn5);
            btn6=(Button) findViewById(R.id.btn6);
            btn7=(Button) findViewById(R.id.btn7);
            btn8=(Button) findViewById(R.id.btn8);
            btn9=(Button) findViewById(R.id.btn9);
            btnAdd=(Button) findViewById(R.id.btnAdd);
            btnSub=(Button) findViewById(R.id.btnSub);
            btnMul=(Button) findViewById(R.id.btnMul);
            btnDiv=(Button) findViewById(R.id.btnDiv);
            btnDot=(Button) findViewById(R.id.btnDot);
            btnSign=(Button) findViewById(R.id.btnSign);
            btnAns=(Button) findViewById(R.id.btnAns);
            btnCE=(Button) findViewById(R.id.btnCE);
            btnC=(Button) findViewById(R.id.btnC);
            btnDel=(Button) findViewById(R.id.btnDel);
            num1=0; num2=0; num=0;
            signFlag=false; numFlag=false;
            //Initializing variables ends here

            //Setting onClickListner
            btn0.setOnClickListener(this);
            btn1.setOnClickListener(this);
            btn2.setOnClickListener(this);
            btn3.setOnClickListener(this);
            btn4.setOnClickListener(this);
            btn5.setOnClickListener(this);
            btn6.setOnClickListener(this);
            btn7.setOnClickListener(this);
            btn8.setOnClickListener(this);
            btn9.setOnClickListener(this);
            btnAdd.setOnClickListener(this);
            btnDiv.setOnClickListener(this);
            btnSub.setOnClickListener(this);
            btnMul.setOnClickListener(this);
            btnSign.setOnClickListener(this);
            btnAns.setOnClickListener(this);
            btnDot.setOnClickListener(this);
            btnCE.setOnClickListener(this);
            btnC.setOnClickListener(this);
            btnDel.setOnClickListener(this);
            //Setting onClickListner Ends here
        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.main, menu);
            return true;
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            int id = item.getItemId();
            if (id == R.id.action_settings) {
                return true;
            }
            return super.onOptionsItemSelected(item);
        }

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            int id =v.getId(); //NullPointerException somewhere around here
            switch (id) {
            case R.id.btn0:
                printNum('0');
                break;
            case R.id.btn1:
                printNum('1');
                break;
            case R.id.btn2:
                printNum('2');
                break;  
            case R.id.btn3:
                printNum('3');
                break;
            case R.id.btn4:
                printNum('4');
                break;  
            case R.id.btn5:
                printNum('5');
                break;  
            case R.id.btn6:
                printNum('6');
                break;  
            case R.id.btn7:
                printNum('7');
                break;  
            case R.id.btn8:
                printNum('8');
                break;  
            case R.id.btn9:
                printNum('9');
                break;  
            case R.id.btnAdd:
                num=Integer.parseInt(et.getText().toString())+num;
                et.setText("");
                signFlag=true;
                last='+';
                break;
            case R.id.btnSub:
                num=Integer.parseInt(et.getText().toString())-num;
                et.setText("");
                signFlag=true;
                last='-';
                break;      
            case R.id.btnMul:
                if(signFlag==false)
                    num=Integer.parseInt(et.getText().toString());
                else
                    num=Integer.parseInt(et.getText().toString())*num;
                et.setText("");
                signFlag=true;
                last='*';
                break;      
            case R.id.btnDiv:
                if(signFlag==false)
                    num=Integer.parseInt(et.getText().toString());
                else
                    num=Integer.parseInt(et.getText().toString())/num;
                et.setText("");
                signFlag=true;
                last='/';
                break;      
            case R.id.btnDot:
                et.setText(et.getText().toString()+".");
                break;      
            case R.id.btnSign:
                double temp=Integer.parseInt(et.getText().toString());
                temp=temp*(-1);
                et.setText(temp+"");
                break;  
            case R.id.btnAns:

                break;
            default:
                break;
            }
        }

        public void printNum(char c) {
            String temp="";
            if(numFlag){
                temp=et.getText().toString();
            }
            temp+=c;
            Dialog dialog = new Dialog(this);
            dialog.show();

            et.setText(temp);
        }

    }

The layout file:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout2"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.calculator.MainActivity" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <EditText
            android:id="@+id/ET"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:ems="10"
            android:inputType="numberDecimal" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btnCE"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="CE" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btnC"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="C" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btnDel"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="DEL" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btnDiv"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="/" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btn7"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="7" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btn8"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="8" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btn9"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="9" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btnMul"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="*" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btn4"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="4" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btn5"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="5" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btn6"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="6" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btnSub"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="-" />
    </LinearLayout> 

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btn1"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="1" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btn2"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="2" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btn3"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="3" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btnAdd"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="+" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btnSign"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="+-" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btn0"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="0" />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btnDot"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="." />

        <Button style="?android:attr/buttonBarButtonStyle"
            android:id="@+id/btnAns"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:text="=" />

    </LinearLayout>

</LinearLayout>

The logcat:

07-18 08:12:03.890: D/gralloc_goldfish(962): Emulator without GPU emulation detected.
07-18 08:12:06.580: D/AndroidRuntime(962): Shutting down VM
07-18 08:12:06.580: W/dalvikvm(962): threadid=1: thread exiting with uncaught exception (group=0xb4ab0ba8)
07-18 08:12:06.580: E/AndroidRuntime(962): FATAL EXCEPTION: main
07-18 08:12:06.580: E/AndroidRuntime(962): Process: com.example.calculator, PID: 962
07-18 08:12:06.580: E/AndroidRuntime(962): java.lang.NullPointerException
07-18 08:12:06.580: E/AndroidRuntime(962):  at com.example.calculator.MainActivity.printNum(MainActivity.java:187)
07-18 08:12:06.580: E/AndroidRuntime(962):  at com.example.calculator.MainActivity.onClick(MainActivity.java:103)
07-18 08:12:06.580: E/AndroidRuntime(962):  at android.view.View.performClick(View.java:4438)
07-18 08:12:06.580: E/AndroidRuntime(962):  at android.view.View$PerformClick.run(View.java:18422)
07-18 08:12:06.580: E/AndroidRuntime(962):  at android.os.Handler.handleCallback(Handler.java:733)
07-18 08:12:06.580: E/AndroidRuntime(962):  at android.os.Handler.dispatchMessage(Handler.java:95)
07-18 08:12:06.580: E/AndroidRuntime(962):  at android.os.Looper.loop(Looper.java:136)
07-18 08:12:06.580: E/AndroidRuntime(962):  at android.app.ActivityThread.main(ActivityThread.java:5001)
07-18 08:12:06.580: E/AndroidRuntime(962):  at java.lang.reflect.Method.invokeNative(Native Method)
07-18 08:12:06.580: E/AndroidRuntime(962):  at java.lang.reflect.Method.invoke(Method.java:515)
07-18 08:12:06.580: E/AndroidRuntime(962):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
07-18 08:12:06.580: E/AndroidRuntime(962):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
07-18 08:12:06.580: E/AndroidRuntime(962):  at dalvik.system.NativeStart.main(Native Method)
07-18 08:12:09.940: I/Process(962): Sending signal. PID: 962 SIG: 9

stacktrace? layout file, show us what u got, makes it a lot easier to help — finki, Jul 18 '16 at 12:05
@MichaelSpitsin I agree with you... It seems that et is always null — guipivoto, Jul 18 '16 at 12:14
Above the line `btn0=(Button) findViewById(R.id.btn0);` Put this line- `et=(EditText) findViewById(R.id.ET);` As you are missing to initialize your `EditText` it is throwing `NullPointerException` — Jimit Patel, Jul 18 '16 at 12:25

score 1 · Accepted Answer · edited Jul 18 '16 at 13:08

1

You might be missing these two:

Instead of switch(id) use this

 public void clicker(View v) {
      switch (v.getId()) {
          case R.id.btnmhome:
               cf.gohome();
               break;
            }
        }

And write

android:onClick="clicker"

it means your method name where you are writing onclick funtion

edited Jul 18 '16 at 13:08

Sanoop Surendran

3,484
4
28
49

answered Jul 18 '16 at 12:12

Punithapriya

131
9

Previously it was switch(v.getId() ) but then I found somewhere they took int id=v.getId() so I tried it. And there are multiple buttons so I implemented a listner instead of changing the onClick property in xml – Kishan Shah Jul 18 '16 at 12:19
you forgot your edittext id to define in oncreate. – Kishan patel Jul 18 '16 at 12:22
See you didnt initialze Edit text variable.Just do declaration for edittext like other views. – Punithapriya Jul 18 '16 at 12:23

Android null pointer exception on view.getId()

1 Answers1