title: Error: java.lang.UnsupportedOperationException: Can't convert to dimension: type=0x3
body: <p>I'm making a simply app for android.
  But if I want to run my app I get a error:</p>
  
  <pre><code>08-15 09:39:33.050: E/AndroidRuntime(871): FATAL EXCEPTION: main
  08-15 09:39:33.050: E/AndroidRuntime(871): Process: com.a3gaatleren, PID: 871
  08-15 09:39:33.050: E/AndroidRuntime(871): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.a3gaatleren/com.a3gaatleren.MainActivity}: java.lang.UnsupportedOperationException: Can't convert to dimension: type=0x3
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.app.ActivityThread.access$800(ActivityThread.java:135)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.os.Handler.dispatchMessage(Handler.java:102)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.os.Looper.loop(Looper.java:136)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.app.ActivityThread.main(ActivityThread.java:5001)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at java.lang.reflect.Method.invokeNative(Native Method)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at java.lang.reflect.Method.invoke(Method.java:515)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at dalvik.system.NativeStart.main(Native Method)
  08-15 09:39:33.050: E/AndroidRuntime(871): Caused by: java.lang.UnsupportedOperationException: Can't convert to dimension: type=0x3
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.content.res.TypedArray.getDimensionPixelSize(TypedArray.java:464)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.view.ViewGroup$MarginLayoutParams.&lt;init&gt;(ViewGroup.java:6129)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.widget.FrameLayout$LayoutParams.&lt;init&gt;(FrameLayout.java:615)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.widget.FrameLayout.generateLayoutParams(FrameLayout.java:559)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.widget.FrameLayout.generateLayoutParams(FrameLayout.java:56)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.view.LayoutInflater.inflate(LayoutInflater.java:480)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.view.LayoutInflater.inflate(LayoutInflater.java:397)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.view.LayoutInflater.inflate(LayoutInflater.java:353)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:249)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:106)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at com.a3gaatleren.MainActivity.onCreate(MainActivity.java:17)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.app.Activity.performCreate(Activity.java:5231)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
  08-15 09:39:33.050: E/AndroidRuntime(871):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
  08-15 09:39:33.050: E/AndroidRuntime(871):  ... 11 more
  08-15 09:39:38.860: I/Process(871): Sending signal. PID: 871 SIG: 9
  </code></pre>
  
  <p>Mainactivity:</p>
  
  <pre><code>package com.a3gaatleren;
  
  import android.support.v7.app.ActionBarActivity;
  import android.content.Intent;
  import android.os.Bundle;
  import android.view.Menu;
  import android.view.MenuItem;
  import android.view.View;
  import android.webkit.WebView;
  import android.widget.Button;
  
  public class MainActivity extends ActionBarActivity {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
      final Button button = (Button) findViewById(R.id.button1);
      button.setOnClickListener(new View.OnClickListener() {
          public void onClick(View v) {
          startActivity(new Intent(MainActivity.this, Samenvattingen.class));
  
          }
      }
      );
  
      }
  
      @Override
      public boolean onCreateOptionsMenu(Menu menu) {
          // Inflate the menu; this adds items to the action bar if it is present.
          getMenuInflater().inflate(R.menu.main, menu);
          return true;
      }
  
      @Override
      public boolean onOptionsItemSelected(MenuItem item) {
          // Handle action bar item clicks here. The action bar will
          // automatically handle clicks on the Home/Up button, so long
          // as you specify a parent activity in AndroidManifest.xml.
          int id = item.getItemId();
          if (id == R.id.action_settings) {
              Intent menuIntent = new Intent(this, Instellingen.class);
              startActivity(menuIntent);
  
              return true;
          }
          return super.onOptionsItemSelected(item);
  
  
      }
  
  
  }
  </code></pre>
  
  <p>activity_main.xml</p>
  
  <pre><code>&lt;RelativeLayout 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:layout_marginLeft="@string/marginbutton"
      android:layout_marginRight="@string/marginbutton"
      tools:context="com.a3gaatleren.MainActivity" &gt;
  
      &lt;Button
      android:id="@+id/button1"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_alignParentLeft="true"
      android:layout_alignParentTop="true"
      android:layout_marginTop="82dp"
      android:text="@string/Samenvatting" /&gt;
  
      &lt;Button
      android:id="@+id/button2"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_alignParentLeft="true"
      android:layout_below="@+id/button1"
      android:text="@string/Woordenlijst" /&gt;
  
      &lt;Button
      android:id="@+id/button3"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_alignParentLeft="true"
      android:layout_below="@+id/button2"
      android:text="@string/Agenda" /&gt;
  
      &lt;Button
      android:id="@+id/button4"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_alignParentLeft="true"
      android:layout_below="@+id/button3"
      android:text="@string/Instellingen" /&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>Can someone tell me how to solve this problem?</p>
  
  <p>PS: English is not my first language, so I don't now of the English is correct </p>