WebView.javaScriptEnable(true); null pointer exception error at android

Question

I'm trying to write a simple calculator. I have a SimpleActivity class which looks like this:

package org.muzzy.calc;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.webkit.WebChromeClient;
import android.webkit.WebView;
import android.widget.Button;

public class SimpleActivity extends Activity implements OnClickListener {
/** Called when the activity is first created. */
private WebView numer;
private Button guzik;
private StringBuilder wys;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    numer = (WebView) findViewById(R.id.webview);
    numer.getSettings().setJavaScriptEnabled(true);
    numer.setWebChromeClient(new WebChromeClient());

    guzik = (Button) findViewById(R.id.button0);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.button1);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.button2);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.button3);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.button4);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.button5);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.button6);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.button7);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.button8);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.button9);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.plus);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.minus);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.multi);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.divide);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.leftP);
    guzik.setOnClickListener(this);
    guzik = (Button) findViewById(R.id.rightP);
    guzik.setOnClickListener(this);
}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    StringBuilder wyr = new StringBuilder();

    switch (v.getId()) {
    case R.id.bs:
        if (wyr.length() > 0)
            wyr.deleteCharAt(wyr.length() - 1);
        break;
    case R.id.ac:
        if (wyr.length() > 0)
            wyr.delete(0, wyr.length());
        break;
    default:
        wyr.append(((Button) v).getText());
    }

    wys.append("<html><body>");
    wys.append("<script type=\"text/javascript\">document.write('");
    wys.append(wyr.toString());
    wys.append("');");
    wys.append("document.write('<br />=' + eval(\"");
    wys.append(wyr.toString());
    wys.append("\"));</script>");
    wys.append("</body></html>");

    numer.loadData(wys.toString(), "application/xhtml", "UTF-8");
}

}

I'm starting that class from another Activity class like this:

Intent simpleIntent = new Intent(this, SimpleActivity.class);
            startActivity(simpleIntent);

When I'm trying to run the project on VM Android 2.3.3 I get this errors:

03-07 21:52:36.624: D/AndroidRuntime(411): Shutting down VM
03-07 21:52:36.624: W/dalvikvm(411): threadid=1: thread exiting with uncaught exception (group=0x40015560)
03-07 21:52:36.634: E/AndroidRuntime(411): FATAL EXCEPTION: main
03-07 21:52:36.634: E/AndroidRuntime(411): java.lang.RuntimeException: Unable to start activity ComponentInfo{org.muzzy.calc/org.muzzy.calc.SimpleActivity}: java.lang.NullPointerException
03-07 21:52:36.634: E/AndroidRuntime(411):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
03-07 21:52:36.634: E/AndroidRuntime(411):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
03-07 21:52:36.634: E/AndroidRuntime(411):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
03-07 21:52:36.634: E/AndroidRuntime(411):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
03-07 21:52:36.634: E/AndroidRuntime(411):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-07 21:52:36.634: E/AndroidRuntime(411):  at android.os.Looper.loop(Looper.java:123)
03-07 21:52:36.634: E/AndroidRuntime(411):  at android.app.ActivityThread.main(ActivityThread.java:3683)
03-07 21:52:36.634: E/AndroidRuntime(411):  at java.lang.reflect.Method.invokeNative(Native Method)
03-07 21:52:36.634: E/AndroidRuntime(411):  at java.lang.reflect.Method.invoke(Method.java:507)
03-07 21:52:36.634: E/AndroidRuntime(411):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-07 21:52:36.634: E/AndroidRuntime(411):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-07 21:52:36.634: E/AndroidRuntime(411):  at dalvik.system.NativeStart.main(Native Method)
03-07 21:52:36.634: E/AndroidRuntime(411): Caused by: java.lang.NullPointerException
03-07 21:52:36.634: E/AndroidRuntime(411):  at org.muzzy.calc.SimpleActivity.onCreate(SimpleActivity.java:25)
03-07 21:52:36.634: E/AndroidRuntime(411):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-07 21:52:36.634: E/AndroidRuntime(411):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
03-07 21:52:36.634: E/AndroidRuntime(411):  ... 11 more

My xml file for simpleActivity looks like this:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<WebView
    android:id="@+id/webview"
    android:layout_width="fill_parent"
    android:layout_height="50dip"
    android:visibility="visible" />

<TableLayout
    android:id="@+id/tableLayout1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:stretchColumns="0,1,2,3" >

    <TableRow
        android:id="@+id/tableRow1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >

        <Button
            android:id="@+id/button1"
            android:text="@string/b1" />

        <Button
            android:id="@+id/button2"
            android:text="@string/b2" />

        <Button
            android:id="@+id/button3"
            android:text="@string/b3" />

        <Button
            android:id="@+id/plus"
            android:text="@string/plus" />
    </TableRow>

    <TableRow
        android:id="@+id/tableRow2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >

        <Button
            android:id="@+id/button4"
            android:text="@string/b4" />

        <Button
            android:id="@+id/button5"
            android:text="@string/b5" />

        <Button
            android:id="@+id/button6"
            android:text="@string/b6" />

        <Button
            android:id="@+id/minus"
            android:text="@string/minus" />
    </TableRow>

    <TableRow
        android:id="@+id/tableRow3"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button
            android:id="@+id/button7"
            android:text="@string/b7" />

        <Button
            android:id="@+id/button8"
            android:text="@string/b8" />

        <Button
            android:id="@+id/button9"
            android:text="@string/b9" />

        <Button
            android:id="@+id/multi"
            android:text="@string/multi" />
    </TableRow>

    <TableRow
        android:id="@+id/tableRow4"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button
            android:id="@+id/leftP"
            android:text="@string/leftParen" />

        <Button
            android:id="@+id/button0"
            android:text="@string/b0" />

        <Button
            android:id="@+id/rightP"
            android:text="@string/rightParen" />

        <Button
            android:id="@+id/divide"
            android:text="@string/divide" />
    </TableRow>

    <TableRow
        android:id="@+id/tableRow5"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button
            android:id="@+id/bs"
            android:text="@string/backspace" />

        <Button
            android:id="@+id/dot"
            android:text="@string/dot" />

        <Button
            android:id="@+id/ac"
            android:text="@string/allclear" />

        <Button
            android:id="@+id/equals"
            android:text="@string/equals" />
    </TableRow>
</TableLayout>

</LinearLayout>

I read a bunch of tutorials and threads at lot of forums and still nothing. What am I doing wrong??

Did you add your new activity(.SimpleActivity) to the Manifest? — Maxim
– Maxim, Commented Mar 7, 2012 at 22:36
Seems weird. Try a project->clean. What is line 25 in your editor? — Amokrane Chentir
– Amokrane Chentir, Commented Mar 7, 2012 at 22:40
I add activity in Manifest like this: <activity android:name=".SimpleActivity" > </activity> and the line which causes the probliem is: numer.getSettings().setJavaScriptEnabled(true); — MuzzY
– MuzzY, Commented Mar 8, 2012 at 20:06

MuzzY · Accepted Answer · 2012-03-11 10:00:30Z

1

Like in most cases it was a simple mistake. My layout for SimpleActivity is not main but simple. There is no webview in the main layout so it doesn't work and return null pointer exception.

answered Mar 11, 2012 at 10:00

MuzzY

314 bronze badges

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Comments

Helper · Accepted Answer · 2012-03-08 11:49:00Z

0

Double click in the Log Cat window on this line: 03-07 21:52:36.634: E/AndroidRuntime(411): at org.muzzy.calc.SimpleActivity.onCreate(SimpleActivity.java:25)

That will bring you at the source line which causes the problem.

Further you forgot a statement wys = new StringBuilder();

And forgot to clear it a a new toch of a button

answered Mar 8, 2012 at 11:49

Helper

912 bronze badges

1 Comment

MuzzY Over a year ago

Thanks for answer. When I was posting my question I was very tired and i forgot to wrote that the line which causes the problem is: numer.getSettings().setJavaScriptEnabled(true);

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