Unfortunately my app has stopped in Android Emulator

I've been looking for an answer for hours now, but my calculator wont work at all :(

I appreciate if you could help me. I've posted the manifest code below. Inform me if you need to see the MainActivity.java or anything else :)

    <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.elof_calc_2000_dragonslayerxx"
android:versionCode="1"
android:versionName="1.0" >

 <uses-sdk
    android:minSdkVersion="15"
    android:targetSdkVersion="17" />

 <application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
     android:name="com.example.elof_calc_2000_dragonslayerxx.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
 </application>

</manifest>

The errors shown on Logcat

03-16 18:09:59.890: E/AndroidRuntime(895): FATAL EXCEPTION: main
03-16 18:09:59.890: E/AndroidRuntime(895): Process: com.example.elof_calc_2000_dragonslayerxx,     PID: 895
03-16 18:09:59.890: E/AndroidRuntime(895): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.elof_calc_2000_dragonslayerxx/com.example.elof_calc_2000_dragonslayerxx.MainActivity}: java.lang.NullPointerException
03-16 18:09:59.890: E/AndroidRuntime(895):  at  android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-16 18:09:59.890: E/AndroidRuntime(895):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-16 18:09:59.890: E/AndroidRuntime(895):  at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-16 18:09:59.890: E/AndroidRuntime(895):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-16 18:09:59.890: E/AndroidRuntime(895):  at android.os.Handler.dispatchMessage(Handler.java:102)
03-16 18:09:59.890: E/AndroidRuntime(895):  at android.os.Looper.loop(Looper.java:136)
03-16 18:09:59.890: E/AndroidRuntime(895):  at android.app.ActivityThread.main(ActivityThread.java:5017)
03-16 18:09:59.890: E/AndroidRuntime(895):  at java.lang.reflect.Method.invokeNative(Native Method)
03-16 18:09:59.890: E/AndroidRuntime(895):  at java.lang.reflect.Method.invoke(Method.java:515)
03-16 18:09:59.890: E/AndroidRuntime(895):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-16 18:09:59.890: E/AndroidRuntime(895):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-16 18:09:59.890: E/AndroidRuntime(895):  at dalvik.system.NativeStart.main(Native Method)
03-16 18:09:59.890: E/AndroidRuntime(895): Caused by: java.lang.NullPointerException
03-16 18:09:59.890: E/AndroidRuntime(895):  at com.example.elof_calc_2000_dragonslayerxx.MainActivity.onClickListeners(MainActivity.java:49)
03-16 18:09:59.890: E/AndroidRuntime(895):  at com.example.elof_calc_2000_dragonslayerxx.MainActivity.onCreate(MainActivity.java:22)
03-16 18:09:59.890: E/AndroidRuntime(895):  at android.app.Activity.performCreate(Activity.java:5231)
03-16 18:09:59.890: E/AndroidRuntime(895):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-16 18:09:59.890: E/AndroidRuntime(895):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
03-16 18:09:59.890: E/AndroidRuntime(895):  ... 11 more
03-16 18:16:23.316: E/AndroidRuntime(1100): FATAL EXCEPTION: main
03-16 18:16:23.316: E/AndroidRuntime(1100): Process: com.example.elof_calc_2000_dragonslayerxx, PID: 1100
03-16 18:16:23.316: E/AndroidRuntime(1100): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.elof_calc_2000_dragonslayerxx/com.example.elof_calc_2000_dragonslayerxx.MainActivity}: java.lang.NullPointerException
03-16 18:16:23.316: E/AndroidRuntime(1100):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at android.os.Handler.dispatchMessage(Handler.java:102)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at android.os.Looper.loop(Looper.java:136)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at android.app.ActivityThread.main(ActivityThread.java:5017)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at java.lang.reflect.Method.invokeNative(Native Method)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at java.lang.reflect.Method.invoke(Method.java:515)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at dalvik.system.NativeStart.main(Native Method)
03-16 18:16:23.316: E/AndroidRuntime(1100): Caused by: java.lang.NullPointerException
03-16 18:16:23.316: E/AndroidRuntime(1100):     at com.example.elof_calc_2000_dragonslayerxx.MainActivity.onClickListeners(MainActivity.java:49)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at com.example.elof_calc_2000_dragonslayerxx.MainActivity.onCreate(MainActivity.java:22)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at android.app.Activity.performCreate(Activity.java:5231)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-16 18:16:23.316: E/AndroidRuntime(1100):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
03-16 18:16:23.316: E/AndroidRuntime(1100):     ... 11 more