title: whenever application is executed it is displayed as blank in android emulator
body: <p>Below i have pasted copy of my java,xml and logcat of the application.</p>
  
  <h2>Here goes my java code</h2>
  
  <hr>
  
  <pre><code>package my.example.myproject;
  
  import my.example.myproject.util.SystemUiHider;
  
  import android.annotation.TargetApi;
  import android.app.Activity;
  import android.content.Intent;
  import android.os.Build;
  import android.os.Bundle;
  import android.os.Handler;
  import android.view.MotionEvent;
  import android.view.View;
  import android.widget.Button;
  
  /**
   * An example full-screen activity that shows and hides the system UI (i.e.
   * status bar and navigation/system bar) with user interaction.
   * 
   * @see SystemUiHider
   */
  public class FullscreenActivity extends Activity {
      /**
       * Whether or not the system UI should be auto-hidden after
       * {@link #AUTO_HIDE_DELAY_MILLIS} milliseconds.
       */
      private static final boolean AUTO_HIDE = true;
  
      /**
       * If {@link #AUTO_HIDE} is set, the number of milliseconds to wait after
       * user interaction before hiding the system UI.
       */
      private static final int AUTO_HIDE_DELAY_MILLIS = 3000;
  
      /**
       * If set, will toggle the system UI visibility upon interaction. Otherwise,
       * will show the system UI visibility upon interaction.
       */
      private static final boolean TOGGLE_ON_CLICK = true;
  
      /**
       * The flags to pass to {@link SystemUiHider#getInstance}.
       */
      private static final int HIDER_FLAGS = SystemUiHider.FLAG_HIDE_NAVIGATION;
  
      /**
       * The instance of the {@link SystemUiHider} for this activity.
       */
      private SystemUiHider mSystemUiHider;
      Button iol,help,about;
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_fullscreen);
          final View controlsView = findViewById(R.id.fullscreen_content_controls);
          iol = (Button)findViewById(R.id.iolCalculation);
          help = (Button)findViewById(R.id.sHelp);
          about = (Button)findViewById(R.id.sAbout);
          Thread iolthread=new Thread(){
              public void run(){
                  try{
                      iol.setOnClickListener(new View.OnClickListener() {
  
  
                              @Override
                              public void onClick(View v) {
                                  // TODO Auto-generated method stub
                                  setContentView(R.layout.selection);
                              }
                      });
                      Intent iolIntent=new Intent(FullscreenActivity.this,Selection.class);
                      startActivity(iolIntent);
                  }
                  finally{
                      finish();
                  }
              }
          };  
          iolthread.start();
          // Set up an instance of SystemUiHider to control the system UI for
          // this activity.
          mSystemUiHider = SystemUiHider.getInstance(this, controlsView,
                  HIDER_FLAGS);
          mSystemUiHider.setup();
          mSystemUiHider
                  .setOnVisibilityChangeListener(new SystemUiHider.OnVisibilityChangeListener() {
                      // Cached values.
                      int mControlsHeight;
                      int mShortAnimTime;
  
                      @Override
                      @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
                      public void onVisibilityChange(boolean visible) {
                          if (Build.VERSION.SDK_INT &gt;= Build.VERSION_CODES.HONEYCOMB_MR2) {
                              // If the ViewPropertyAnimator API is available
                              // (Honeycomb MR2 and later), use it to animate the
                              // in-layout UI controls at the bottom of the
                              // screen.
                              if (mControlsHeight == 0) {
                                  mControlsHeight = controlsView.getHeight();
                              }
                              if (mShortAnimTime == 0) {
                                  mShortAnimTime = getResources().getInteger(
                                          android.R.integer.config_shortAnimTime);
                              }
                              controlsView
                                      .animate()
                                      .translationY(visible ? 0 : mControlsHeight)
                                      .setDuration(mShortAnimTime);
                          } else {
                              // If the ViewPropertyAnimator APIs aren't
                              // available, simply show or hide the in-layout UI
                              // controls.
                              controlsView.setVisibility(visible ? View.VISIBLE
                                      : View.GONE);
                          }
  
                          if (visible &amp;&amp; AUTO_HIDE) {
                              // Schedule a hide().
                              delayedHide(AUTO_HIDE_DELAY_MILLIS);
                          }
                      }
                  });
  
          // Set up the user interaction to manually show or hide the system UI.
          controlsView.setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View view) {
                  if (TOGGLE_ON_CLICK) {
                      mSystemUiHider.toggle();
                  } else {
                      mSystemUiHider.show();
                  }
              }
          });
  
          // Upon interacting with UI controls, delay any scheduled hide()
          // operations to prevent the jarring behavior of controls going away
          // while interacting with the UI.
  
      }
  
      @Override
      protected void onPostCreate(Bundle savedInstanceState) {
          super.onPostCreate(savedInstanceState);
  
          // Trigger the initial hide() shortly after the activity has been
          // created, to briefly hint to the user that UI controls
          // are available.
          delayedHide(100);
      }
  
      /**
       * Touch listener to use for in-layout UI controls to delay hiding the
       * system UI. This is to prevent the jarring behavior of controls going away
       * while interacting with activity UI.
       */
      View.OnTouchListener mDelayHideTouchListener = new View.OnTouchListener() {
          @Override
          public boolean onTouch(View view, MotionEvent motionEvent) {
              if (AUTO_HIDE) {
                  delayedHide(AUTO_HIDE_DELAY_MILLIS);
              }
              return false;
          }
      };
  
      Handler mHideHandler = new Handler();
      Runnable mHideRunnable = new Runnable() {
          @Override
          public void run() {
              mSystemUiHider.hide();
          }
      };
  
      /**
       * Schedules a call to hide() in [delay] milliseconds, canceling any
       * previously scheduled calls.
       */
      private void delayedHide(int delayMillis) {
          mHideHandler.removeCallbacks(mHideRunnable);
          mHideHandler.postDelayed(mHideRunnable, delayMillis);
      }
  }
  </code></pre>
  
  <hr>
  
  <h2>XML</h2>
  
  <pre><code>&lt;FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:background="@color/black"
      tools:context=".FullscreenActivity" 
      android:id="@+id/frame_layout"&gt;
  
          &lt;LinearLayout
              android:id="@+id/fullscreen_content_controls"
              style="?buttonBarStyle"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_gravity="bottom|center_horizontal"
              android:background="@color/black_overlay"
              android:orientation="horizontal"
              tools:ignore="UselessParent" &gt;
          &lt;/LinearLayout&gt;
  
          &lt;Button
              style="@style/ButtonBarButton"
              android:layout_width="222dp"
              android:layout_height="62dp"
              android:layout_marginLeft="45dp"
              android:layout_marginTop="75dp"
              android:background="@color/black"
              android:paddingLeft="20dp"
              android:id="@+id/iolCalculation"
              android:text="@string/Button"
              android:textColor="@color/WhiteSmoke"
              android:textStyle="bold" /&gt;
  
          &lt;Button
              style="@style/ButtonBarButton"
              android:layout_width="222dp"
              android:layout_height="62dp"
              android:layout_marginLeft="45dp"
              android:id="@+id/sHelp"
              android:layout_marginTop="139dp"
              android:background="@color/Black"
              android:gravity="center"
              android:paddingLeft="10dp"
              android:text="@string/Button1"
              android:textColor="@color/WhiteSmoke"
              android:textStyle="bold" /&gt;
  
          &lt;Button
              style="@style/ButtonBarButton"
              android:layout_width="222dp"
              android:layout_height="62dp"
              android:id="@+id/sAbout"
              android:layout_marginLeft="45dp"
              android:layout_marginTop="203dp"
              android:background="@color/Black"
              android:paddingLeft="10dp"
              android:text="@string/Button2"
              android:textColor="@color/WhiteSmoke"
              android:textStyle="bold" &gt;
  
          &lt;/Button&gt;
  &lt;/FrameLayout&gt;
  </code></pre>
  
  <hr>
  
  <h2>logcat</h2>
  
  <pre><code>12-16 10:48:26.975: E/Trace(767): error opening trace file: No such file or directory (2)
  12-16 10:51:38.199: E/AndroidRuntime(767): FATAL EXCEPTION: main
  12-16 10:51:38.199: E/AndroidRuntime(767): java.lang.NullPointerException
  12-16 10:51:38.199: E/AndroidRuntime(767):  at com.android.internal.widget.ActionBarView$3.onClick(ActionBarView.java:168)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at android.view.View.performClick(View.java:4202)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at android.view.View$PerformClick.run(View.java:17340)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at android.os.Handler.handleCallback(Handler.java:725)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at android.os.Handler.dispatchMessage(Handler.java:92)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at android.os.Looper.loop(Looper.java:137)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at android.app.ActivityThread.main(ActivityThread.java:5039)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at java.lang.reflect.Method.invokeNative(Native Method)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at java.lang.reflect.Method.invoke(Method.java:511)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
  12-16 10:51:38.199: E/AndroidRuntime(767):  at dalvik.system.NativeStart.main(Native Method)
  </code></pre>
  
  <hr>
  
  <p><strong>i have tried every possible solution in stackoverflow but in vain.help me. I think mostly there is a problem in xml to java display content.Also do i need to put in id for every layout in xml and how does the java code detect the layout to be displayed</strong></p>
  
  <p><strong>here goes my selection java code and xml</strong></p>
  
  <pre><code>    package com.example.iolcalci;
  
  import android.app.Activity;
  import android.os.Bundle;
  
  public class Selection extends Activity {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          // TODO Auto-generated method stub
          super.onCreate(savedInstanceState);
          setContentView(R.layout.selective);
  
      }
  
  }
  </code></pre>
  
  <hr>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:background="@color/black"
      android:orientation="vertical" &gt;
  
      &lt;Spinner
          android:id="@+id/formulae"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_marginLeft="50dp"
          android:layout_marginRight="50dp"
          android:background="@color/LightSkyBlue"
          android:prompt="@string/prompt"
          android:entries="@array/formulas" /&gt;
  
      &lt;TextView
          android:id="@+id/k2"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_alignRight="@+id/k1"
          android:layout_below="@+id/k1"
          android:layout_marginTop="38dp"
          android:text="@string/K2"
          android:textColor="@color/White"
          android:textSize="25sp" /&gt;
  
      &lt;TextView
          android:id="@+id/al_const"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_alignLeft="@+id/al"
          android:layout_below="@+id/al"
          android:layout_marginTop="44dp"
          android:text="@string/Rx"
          android:textColor="@color/White"
          android:textSize="20sp" /&gt;
  
      &lt;TextView
          android:id="@+id/al"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_alignRight="@+id/k2"
          android:layout_below="@+id/k2"
          android:layout_marginTop="38dp"
          android:text="@string/AL"
          android:textColor="@color/White"
          android:textSize="25sp" /&gt;
  
      &lt;EditText
          android:id="@+id/k2_editText"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_above="@+id/al"
          android:layout_alignRight="@+id/al_editText"
          android:layout_alignTop="@+id/k2"
          android:layout_marginLeft="120dp"
          android:background="@color/black"
          android:ems="10"
          android:inputType="numberDecimal"
          android:textColorLink="@color/white" /&gt;
  
      &lt;EditText
          android:id="@+id/al_editText"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_alignRight="@+id/formulae"
          android:layout_alignTop="@+id/al"
          android:layout_marginLeft="120dp"
          android:ems="10"
          android:inputType="numberDecimal" /&gt;
  
      &lt;EditText
          android:id="@+id/al_const_editText"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_alignBottom="@+id/al_const"
          android:layout_alignRight="@+id/al_editText"
          android:layout_marginLeft="120dp"
          android:ems="10"
          android:inputType="numberDecimal" /&gt;
  
      &lt;Button
          android:id="@+id/result"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_alignParentBottom="true"
          android:layout_centerHorizontal="true"
          android:background="@color/LightSkyBlue"
          android:text="@string/Result" /&gt;
  
      &lt;EditText
          android:id="@+id/k1_editText"
          android:layout_width="wrap_content"
          android:layout_height="37dp"
          android:layout_alignLeft="@+id/k2_editText"
          android:layout_alignRight="@+id/formulae"
          android:layout_below="@+id/formulae"
          android:layout_marginTop="30dp"
          android:background="@color/black"
          android:ems="10"
          android:inputType="numberDecimal"
          android:textColorLink="@color/White" /&gt;
  
      &lt;TextView
          android:id="@+id/k1"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_alignBottom="@+id/k1_editText"
          android:layout_alignParentLeft="true"
          android:layout_marginLeft="27dp"
          android:text="@string/K1"
          android:textColor="@color/white"
          android:textSize="25sp" /&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>THE NEW LOGCAT </p>
  
  <hr>
  
  <pre><code>   12-21 10:44:50.419: W/Trace(766): Unexpected value from nativeGetEnabledTags: 0
  12-21 10:44:50.573: W/Trace(766): Unexpected value from nativeGetEnabledTags: 0
  12-21 10:44:50.573: W/Trace(766): Unexpected value from nativeGetEnabledTags: 0
  12-21 10:44:50.923: D/AndroidRuntime(766): Shutting down VM
  12-21 10:44:50.923: W/dalvikvm(766): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
  12-21 10:44:50.933: E/AndroidRuntime(766): FATAL EXCEPTION: main
  12-21 10:44:50.933: E/AndroidRuntime(766): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.iolcalci/com.example.iolcalci.MainActivity}: java.lang.NullPointerException
  12-21 10:44:50.933: E/AndroidRuntime(766):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at android.os.Handler.dispatchMessage(Handler.java:99)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at android.os.Looper.loop(Looper.java:137)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at android.app.ActivityThread.main(ActivityThread.java:5039)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at java.lang.reflect.Method.invokeNative(Native Method)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at java.lang.reflect.Method.invoke(Method.java:511)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at dalvik.system.NativeStart.main(Native Method)
  12-21 10:44:50.933: E/AndroidRuntime(766): Caused by: java.lang.NullPointerException
  12-21 10:44:50.933: E/AndroidRuntime(766):  at com.example.iolcalci.MainActivity.onCreate(MainActivity.java:23)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at android.app.Activity.performCreate(Activity.java:5104)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
  12-21 10:44:50.933: E/AndroidRuntime(766):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
  12-21 10:44:50.933: E/AndroidRuntime(766):  ... 11 more
  </code></pre>
  
  <hr>
  
  <p><strong>Manifest file</strong></p>
  
  <pre><code>    &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.example.iolcalci"
      android:versionCode="1"
      android:versionName="1.0" &gt;
  
      &lt;uses-sdk
          android:minSdkVersion="8"
          android:targetSdkVersion="17" /&gt;
  
      &lt;application
          android:allowBackup="true"
          android:icon="@drawable/ic_launcher"
          android:label="@string/app_name"
          android:theme="@style/AppTheme" &gt;
          &lt;activity
              android:name="com.example.iolcalci.MainActivity"
              android:label="@string/app_name" &gt;
              &lt;intent-filter&gt;
                  &lt;action android:name="android.intent.action.MAIN" /&gt;
                  &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
              &lt;/intent-filter&gt;
          &lt;/activity&gt;
          &lt;activity
              android:name="Selection"
              android:exported="false"
              android:configChanges="orientation|keyboardHidden|screenSize"
              android:label="@string/app_name"&gt;
                  &lt;intent-filter&gt;
                  &lt;action android:name="com.example.iolcalci.MAIN" /&gt;
                  &lt;category android:name="android.intent.category.DEFAULT" /&gt;
            &lt;/intent-filter&gt;
          &lt;/activity&gt;
      &lt;/application&gt;
  
  &lt;/manifest&gt;
  </code></pre>