title: how to use custom views in layout xml
body: <p>I've created a custom layout to show gif animated image.
   Here is the code: </p>
  
  <pre><code>public class GIFView extends View{        
  private Movie movie;  
  private InputStream is;  
  private long moviestart;  
  private long duration;
  
  public GIFView(Context context) {  
      super(context);
      is=getResources().openRawResource(R.drawable.anim_cerca);  
      movie=Movie.decodeStream(is);
      duration = movie.duration();
  }  
  
  public GIFView(Context context,AttributeSet set){
      super(context,set);
      is=getResources().openRawResource(R.drawable.anim_cerca);  
      movie=Movie.decodeStream(is);
      duration = movie.duration();
  }
  
  public GIFView(Context context,AttributeSet set,int def){
      super(context,set,def);
      is=getResources().openRawResource(R.drawable.anim_cerca);  
      movie=Movie.decodeStream(is);
      duration = movie.duration();
  }
  
  @Override  
  protected void onDraw(Canvas canvas) {
      super.onDraw(canvas);
      long now=android.os.SystemClock.uptimeMillis();
      Paint p = new Paint();
      p.setAntiAlias(true);
      if (moviestart == 0) 
          moviestart = now;
  
      int relTime = (int)((now - moviestart) % duration);
  
      movie.setTime(relTime);
      movie.draw(canvas,0,0);
  
  
      this.invalidate();
  }                         
  }  
  </code></pre>
  
  <p>This is the xml where i put this object: </p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical" android:layout_width="match_parent"
  android:layout_height="match_parent" android:background="@drawable/sfondo"&gt;
  &lt;LinearLayout android:id="@+id/linearLayout2"
      android:layout_height="wrap_content" android:layout_width="match_parent"
      android:orientation="vertical"&gt;
      &lt;LinearLayout android:id="@+id/linearLayout1"
          android:layout_height="fill_parent" android:weightSum="1"
          android:layout_width="fill_parent" android:orientation="horizontal"&gt;
          &lt;ImageView android:layout_height="73dp" android:id="@+id/imageView1"
              android:layout_weight="0.25" android:src="@drawable/trovachiavi"
              android:layout_width="256dip"&gt;&lt;/ImageView&gt;
          &lt;ImageButton android:id="@+id/infoButton"
              android:background="@null" android:layout_height="47dp"
              android:layout_marginLeft="10dip" android:layout_weight="0.25"
              android:layout_marginTop="15dip" android:src="@drawable/info_mini"
              android:layout_width="47dp"&gt;&lt;/ImageButton&gt;
      &lt;/LinearLayout&gt;
  &lt;/LinearLayout&gt;
  &lt;LinearLayout android:id="@+id/layoutGIF"
      android:layout_height="wrap_content" android:layout_width="wrap_content"
      android:orientation="vertical"&gt;
      &lt;com.digit.GIFView android:id="@+id/gIFView1"
          android:layout_width="wrap_content" android:layout_height="wrap_content"
          android:layout_gravity="center"&gt;&lt;/com.digit.GIFView&gt;
  &lt;/LinearLayout&gt;
  &lt;ImageButton android:id="@+id/avvia_cerca"
      android:layout_height="wrap_content" android:layout_width="wrap_content"
      android:layout_marginTop="10dp" android:layout_gravity="center|bottom"
      android:background="@null"&gt;&lt;/ImageButton&gt;
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>When i go in the Graphical Layout zone of xml, it appears an error:</p>
  
  <pre><code>The following classes could not be instantiated:
  -  (Open Class, Show Error Log)
  See the Error Log (Window &gt; Show View) for more details.
  Tip: Use View.isInEditMode() in your custom views to skip code when shown in Eclipse
  </code></pre>
  
  <p>and in Error log appears these:</p>
  
  <pre><code>java.lang.NullPointerException
  at com.digit.GIFView.&lt;init&gt;(GIFView.java:27)
  at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
  at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
  at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
  at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
  at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.instantiateClass(ProjectCallback.java:396)
  at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.loadView(ProjectCallback.java:164)
  at com.android.layoutlib.bridge.android.BridgeInflater.loadCustomView(BridgeInflater.java:205)
  at com.android.layoutlib.bridge.android.BridgeInflater.createViewFromTag(BridgeInflater.java:133)
  at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:83)
  at android.view.LayoutInflater.rInflate(LayoutInflater.java:702)
  at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:86)
  at android.view.LayoutInflater.rInflate(LayoutInflater.java:702)
  at android.view.LayoutInflater.inflate(LayoutInflater.java:479)
  at android.view.LayoutInflater.inflate(LayoutInflater.java:367)
  at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:324)
  at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:321)
  at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:325)
  at com.android.ide.eclipse.adt.internal.editors.layout.gle2.RenderService.createRenderSession(RenderService.java:380)
  at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.renderWithBridge(GraphicalEditorPart.java:1310)
  at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.recomputeLayout(GraphicalEditorPart.java:1075)
  at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.activated(GraphicalEditorPart.java:901)
  at com.android.ide.eclipse.adt.internal.editors.layout.LayoutEditor.partActivated(LayoutEditor.java:416)
  at com.android.ide.eclipse.adt.internal.editors.layout.LayoutEditor.partBroughtToTop(LayoutEditor.java:425)
  at org.eclipse.ui.internal.PartListenerList$2.run(PartListenerList.java:87)
  at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
  at org.eclipse.core.runtime.Platform.run(Platform.java:888)
  at org.eclipse.ui.internal.PartListenerList.fireEvent(PartListenerList.java:57)
  at org.eclipse.ui.internal.PartListenerList.firePartBroughtToTop(PartListenerList.java:85)
  at org.eclipse.ui.internal.PartService.firePartBroughtToTop(PartService.java:208)
  at org.eclipse.ui.internal.WorkbenchPagePartList.firePartBroughtToTop(WorkbenchPagePartList.java:76)
  at org.eclipse.ui.internal.WorkbenchPagePartList.fireActiveEditorChanged(WorkbenchPagePartList.java:52)
  at org.eclipse.ui.internal.PartList.setActiveEditor(PartList.java:162)
  at org.eclipse.ui.internal.WorkbenchPage.makeActiveEditor(WorkbenchPage.java:1281)
  at org.eclipse.ui.internal.WorkbenchPage.setActivePart(WorkbenchPage.java:3530)
  at org.eclipse.ui.internal.WorkbenchPage.requestActivation(WorkbenchPage.java:3077)
  at org.eclipse.ui.internal.PartPane.requestActivation(PartPane.java:279)
  at org.eclipse.ui.internal.EditorPane.requestActivation(EditorPane.java:98)
  at org.eclipse.ui.internal.PartPane.setFocus(PartPane.java:325)
  at org.eclipse.ui.internal.EditorPane.setFocus(EditorPane.java:127)
  at org.eclipse.ui.internal.PartStack.presentationSelectionChanged(PartStack.java:844)
  at org.eclipse.ui.internal.PartStack.access$1(PartStack.java:827)
  at org.eclipse.ui.internal.PartStack$1.selectPart(PartStack.java:137)
  at org.eclipse.ui.internal.presentations.util.TabbedStackPresentation$1.handleEvent(TabbedStackPresentation.java:133)
  at org.eclipse.ui.internal.presentations.util.AbstractTabFolder.fireEvent(AbstractTabFolder.java:269)
  at org.eclipse.ui.internal.presentations.util.AbstractTabFolder.fireEvent(AbstractTabFolder.java:278)
  at org.eclipse.ui.internal.presentations.defaultpresentation.DefaultTabFolder.access$1(DefaultTabFolder.java:1)
  at org.eclipse.ui.internal.presentations.defaultpresentation.DefaultTabFolder$2.handleEvent(DefaultTabFolder.java:88)
  at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
  at org.eclipse.swt.widgets.Display.sendEvent(Display.java:3783)
  at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1375)
  at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1398)
  at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1383)
  at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1195)
  at org.eclipse.swt.custom.CTabFolder.setSelection(CTabFolder.java:2743)
  at org.eclipse.swt.custom.CTabFolder.onMouse(CTabFolder.java:1429)
  at org.eclipse.swt.custom.CTabFolder$1.handleEvent(CTabFolder.java:257)
  at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
  at org.eclipse.swt.widgets.Display.sendEvent(Display.java:3783)
  at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1375)
  at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1398)
  at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1383)
  at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1195)
  at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3629)
  at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3284)
  at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2640)
  at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2604)
  at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2438)
  at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:671)
  at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
  at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:664)
  at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
  at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:115)
  at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
  at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
  at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
  at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:369)
  at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:597)
  at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:620)
  at org.eclipse.equinox.launcher.Main.basicRun(Main.java:575)
  at org.eclipse.equinox.launcher.Main.run(Main.java:1408)
  </code></pre>
  
  <p>What can i do? where does the error born?
  The elements under my custom view aren't displayed!</p>