title: App Crash when adding
body: <p>I have following issue: I got an Activity in which I wanted to add a Button so I can send Information to my raspberry Pi when clicked.</p>
  
  <p>Now as soon as I included the Button the program crashes when it tries to enter the Activity. Clearing the Project didn't help.</p>
  
  <p>Before I included everything for the Button it worked fine.</p>
  
  <pre><code>import android.app.Activity;
  import android.content.Intent;
  import android.os.Bundle;
  import android.view.MotionEvent;
  import android.view.View;
  import android.widget.Button;
  import android.widget.ImageView;
  import android.widget.TextView;
  
  
  import android.os.AsyncTask;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.net.HttpURLConnection;
  import java.net.URL;
  
  public class CocktailActivity extends Activity {
  
      Button make = (Button) findViewById(R.id.make);
      TextView cocktail_name;
      TextView cocktail_zutaten;
      ImageView cocktail_image_big;
      Intent intent;
  
  
      @Override
      public void onCreate(Bundle icicle) {
          super.onCreate(icicle);
  
          setContentView(R.layout.cocktail_layout);
  
  
          cocktail_name = (TextView) findViewById(R.id.cocktail_name_detail);
          cocktail_zutaten = (TextView) findViewById(R.id.cocktail_zutaten_detail);
          cocktail_image_big = (ImageView) findViewById(R.id.cocktail_image_detail);
  
          intent = getIntent();
          Cocktail cocktail = AppData.cocktailList.get(intent.getIntExtra("cocktailId", 0));
  
          cocktail_name.setText(cocktail.getName());
          cocktail_zutaten.setText(cocktail.getZubereitung());
          cocktail_image_big.setImageDrawable(getResources().getDrawable(R.drawable.ic_cocktail_big_platzhalter));
  
  
          make.setOnClickListener(new View.OnClickListener(){
              @Override
              public void onClick(View v){
                  new Background_get().execute("led1=1");
  
  
              }
          });
      }
  
      private class Background_get extends AsyncTask&lt;String, Void, String&gt; {
          @Override
          protected String doInBackground(String... params) {
              try {
  
                  URL url = new URL("http://192.168.178.34/?" + params[0]);
                  HttpURLConnection connection = (HttpURLConnection) url.openConnection();
  
                  BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                  StringBuilder result = new StringBuilder();
                  String inputLine;
                  while ((inputLine = in.readLine()) != null)
                      result.append(inputLine).append("\n");
  
                  in.close();
                  connection.disconnect();
                  return result.toString();
  
              } catch (IOException e) {
                  e.printStackTrace();
              }
              return null;
          }
  
      }
  
  }
  
  
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  
      &lt;LinearLayout
      android:paddingRight="20dp"
      android:paddingLeft="20dp"
      android:layout_height="fill_parent"
      android:layout_width="fill_parent"
      android:orientation="vertical"
      xmlns:android="http://schemas.android.com/apk/res/android"&gt;
  
      &lt;TextView
          android:layout_height="wrap_content"
          android:layout_width="fill_parent"
          android:textSize="22sp"
          android:id="@+id/cocktail_name_detail"/&gt;
  
  
          &lt;TextView
              android:id="@+id/cocktail_zutaten_detail"
              android:layout_width="match_parent"
              android:layout_height="185dp"
              android:gravity="center" /&gt;
  
      &lt;Button
          android:id="@+id/make"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:text="Make" /&gt;
  
      &lt;ImageView
          android:id="@+id/cocktail_image_detail"
          android:layout_width="match_parent"
          android:layout_height="fill_parent" /&gt;
  
  
  
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>Edit:</p>
  
  <p>The Logcat says at the crash:</p>
  
  <pre><code>                                             --------- beginning of crash
  </code></pre>
  
  <p>03-16 17:00:04.884 2942-2942/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                   Process: com.example.paddy.cocktailapp20, PID: 2942
                                                   java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.paddy.cocktailapp20/com.example.paddy.cocktailapp20.CocktailActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
                                                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2236)
                                                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
                                                       at android.app.ActivityThread.access$800(ActivityThread.java:151)
                                                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
                                                       at android.os.Handler.dispatchMessage(Handler.java:102)
                                                       at android.os.Looper.loop(Looper.java:135)
                                                       at android.app.ActivityThread.main(ActivityThread.java:5254)
                                                       at java.lang.reflect.Method.invoke(Native Method)
                                                       at java.lang.reflect.Method.invoke(Method.java:372)
                                                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
                                                    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
                                                       at android.app.Activity.findViewById(Activity.java:2072)
                                                       at com.example.paddy.cocktailapp20.CocktailActivity.(CocktailActivity.java:22)
                                                       at java.lang.reflect.Constructor.newInstance(Native Method)
                                                       at java.lang.Class.newInstance(Class.java:1606)
                                                       at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
                                                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2226)
                                                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
                                                       at android.app.ActivityThread.access$800(ActivityThread.java:151) 
                                                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
                                                       at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                       at android.os.Looper.loop(Looper.java:135) 
                                                       at android.app.ActivityThread.main(ActivityThread.java:5254) 
                                                       at java.lang.reflect.Method.invoke(Native Method) 
                                                       at java.lang.reflect.Method.invoke(Method.java:372) 
                                                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
  03-16 17:00:04.886 1487-1922/system_process W/ActivityManager:   Force finishing activity 1 com.example.paddy.cocktailapp20/.CocktailActivity
  03-16 17:00:04.887 1487-1922/system_process W/ActivityManager:   Force finishing activity 2 com.example.paddy.cocktailapp20/.MainActivity</p>