Android: Zoom

The SDK offers two ways to achieve zooming the active view.

Existing commands JAVA

Simply using the runCommand() method of the singleton CFxARESInstance.instance().
The final call looks like: CFxARESInstance.instance().runCommand("_ZOOM\n_FIT\n");
This execution can be linked with a onClickListener() of a simple Button. All existing commands take care about refreshing the GA ( graphics area ) properly.

Button.setOnClickListener(new View.OnClickListener()
{
    @Override
    public void onClick(View v)
    {
        CFxARESInstance.instance().runCommand("_ZOOM\n_FIT\n");
      }
});

Hint: The same can be e.g. done with PAN.
Available commands are: -PAN 0,0,0 1,1,1\n , PANUP, PANDOWN, PANLEFT, PANRIGHT

Custom code - Java Native Interface JAVA C++

The other way is to write custom C++ code that requires some more actions but has more potential regarding when and how it is executed. The first step is to specify a native Java method that can be called from the app side but must be implemented on C++ side. This native method can be linked with a onClickListener() of simple Button. When the View is updated programmatically without a core command, it must be executed from the working thread and the refresh of the GA ( graphics area ) must be addressed manually. The JNI method accesses the C++ part of the application and must be executed within the working thread. A suitable method runOnWorkingThread() is provided by CFxARESInstance.instance() .
Refreshing the GA can be achieved with a modeless operation. The modeless helper class CModellessOperationHelper is implemented as a guard. When the object is getting destroyed it takes care about refreshing the graphics area.

public static native void ZoomFit();

Button.setOnClickListener(new View.OnClickListener()
{
    @Override
    public void onClick(View v)
    {
      CFxARESInstance.instance().runOnWorkingThread(new Runnable()
    {
      @Override
        public void run()
        {
          JNI.ZoomFit();
        }
    });
}
});

#include <EditorImpl.h>

struct CModellessOperationHelper
{
    CModellessOperationHelper( CFxDatabase* pDatabase, const CFxString& operationName ) : _operationName( operationName )
    {
        OdEditorImplPtr pEditor = odedEditor();
        pEditor->fire_modelessOperationWillStart( _operationName );

        if ( pDatabase )
            pDatabase->StartUndoRecord(_operationName );
    }

    ~CModellessOperationHelper()
    {
        OdEditorImplPtr pEditor = odedEditor();
        pEditor->fire_modelessOperationEnded( _operationName );
    }

    CFxString _operationName;
    CFxDatabase* _pDatabase;
};

JNIEXPORT void JNICALL Java_com_graebert_dwgeditor_JNI_ZoomFit( JNIEnv * env, jclass clazz );

JNIEXPORT void JNICALL Java_com_graebert_dwgeditor_JNI_ZoomFit( JNIEnv * env, jclass clazz )
{
    if ( 0 == ACTIVE_DOCUMENT() )
        return;

    CFxDatabasePtr pDB = ACTIVE_DOCUMENT()->GetFxDatabase();
    if ( pDB.isNull() )
        return;

    // Start operation, it will be closed automatically.
    CModellessOperationHelper operation( pDB, L"OP_ZOOMFIT" );

    CFxView* pFxView = ACTIVE_DOCUMENT()->GetActiveFxView();
    OdGsView* pView = static_cast<OdGsView*>( pFxView );

    OdGeBoundBlock3d block;
    if ( pFxView->ViewExtentsWCS( block ) )
        pFxView->ZoomExtentsWCS( &block );
    pFxView->EndTransaction();
}