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Asked: 2026-06-08T17:41:54+00:00

I cannot figure out why these 2 buttons are not working, i have a

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I cannot figure out why these 2 buttons are not working, i have a layout file inwhich is created when the user selects a certain theme in my application. With the layout it has a webview it has 2 buttons to goback and goforward. 

   <Button 
    android:id="@+id/button1" 
    android:layout_width="wrap_content" 
    android:text="Back" 
    android:layout_alignParentLeft="true" 
    android:layout_height="wrap_content" 
    android:background="@drawable/button_blue" 
    style="@style/ButtonText">
  </Button>

  <Button 
    android:id="@+id/button2" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_alignParentRight="true" 
    android:background="@drawable/button_blue"
    style="@style/ButtonText" 
    android:text="Forward">
 </Button>


  <WebView
    android:id="@+id/webview01"
    android:layout_width="fill_parent"
    android:layout_height="0dp"
    android:layout_weight="1.12" >

This is not the entire layout file, but here is the bit of stuff i am working with for the webview and the 2 buttons, now inside my main activity here is my button code.

      @Override
public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    if (Prefs.theme.equals("Theme1"))
        setContentView(R.layout.main);
    else if (Prefs.theme.equals("Theme2"))
        setContentView(R.layout.main2);
    else if (Prefs.theme.equals("Theme3"))
        setContentView(R.layout.main3);
    else setContentView(R.layout.main);



    btnForward=(Button) findViewById (R.id.button1);
    btnBackward=(Button) findViewById (R.id.button2);
    btnForward.setOnClickListener(this);
    btnBackward.setOnClickListener(this);


    // more code within on create .....

// Later in the code 

public void onClick(View v) {

    switch(v.getId()) {

        case R.id.button1:
            WebViewClientDemoActivity.web.goBack();
           break;

        case R.id.button2:
            WebViewClientDemoActivity.web.goForward();
           break;
    }

//

I problem im having is by default it loads main.xml not main3 (which is were the 2 buttons are)

LogCat Errors

  07-27 16:00:34.802: E/AndroidRuntime(547): FATAL EXCEPTION: main
  07-27 16:00:34.802: E/AndroidRuntime(547): java.lang.RuntimeException: Unable to start activity       ComponentInfo{com.jaisonbrooks.enlighten/com.jaisonbrooks.enlighten.WebViewClientDemoActivity}: java.lang.NullPointerException
  07-27 16:00:34.802: E/AndroidRuntime(547):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at android.os.Handler.dispatchMessage(Handler.java:99)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at android.os.Looper.loop(Looper.java:123)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at android.app.ActivityThread.main(ActivityThread.java:3683)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at java.lang.reflect.Method.invokeNative(Native Method)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at java.lang.reflect.Method.invoke(Method.java:507)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at dalvik.system.NativeStart.main(Native Method)
  07-27 16:00:34.802: E/AndroidRuntime(547): Caused by: java.lang.NullPointerException
  07-27 16:00:34.802: E/AndroidRuntime(547):    at com.jaisonbrooks.enlighten.WebViewClientDemoActivity.onCreate(WebViewClientDemoActivity.java:75)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
  07-27 16:00:34.802: E/AndroidRuntime(547):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
  07-27 16:00:34.802: E/AndroidRuntime(547):    ... 11 more
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1 Answer

  1. Editorial Team

    First in your onCreate method find your buttons by ids : 

    public class YourActivity extends Activity implements OnClickListener {
Button btnForward;
Button btnBackward;

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

        btnForward=(Button) findViewById (R.id.btnForward);
        btnBackward=(Button) findViewById (R.id.btnBackward);

        //set listeners
        btnForward.setOnClickListener(this);
        btnBackward.setOnClickListener(this);

        // your code here .... 
    }

@Override
public void onClick(View v ) {
     switch(v.getId()) {

        case R.id.btnBackward:
            WebViewClientDemoActivity.web.goBack();
           break;
        case R.id.btnForward:
            WebViewClientDemoActivity.web.goForward();
           break;
    }
}

    }

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