How to use

setTopIndex

method

in

org.eclipse.jface.text.TextViewer

public void setTopIndex(int index) {
  txtViewer.setTopIndex(index);
}

public void showTopOfFile() {
  txtViewer.setTopIndex(0);
}

public void showBottomOfFile() {
  txtViewer.setTopIndex(document.getNumberOfLines());
}

/**
 * Enables the redrawing of this text viewer.
 *
 * @param topIndex the top index to be set or <code>-1</code>
 * @since 3.0
 */
protected void enabledRedrawing(int topIndex) {
  if (fDocumentAdapter instanceof IDocumentAdapterExtension) {
    IDocumentAdapterExtension extension= (IDocumentAdapterExtension) fDocumentAdapter;
    StyledText textWidget= getTextWidget();
    if (textWidget != null && !textWidget.isDisposed()) {
      extension.resumeForwardingDocumentChanges();
      if (topIndex > -1) {
        try {
          setTopIndex(topIndex);
        } catch (IllegalArgumentException x) {
          // changes don't allow for the previous top pixel
        }
      }
    }
  }
  if (fViewerState != null) {
    fViewerState.restore(topIndex == -1);
    fViewerState= null;
  }
  if (fTextWidget != null && !fTextWidget.isDisposed())
    fTextWidget.setRedraw(true);
  fireRedrawChanged();
}

/**
 * Enables the redrawing of this text viewer.
 *
 * @param topIndex the top index to be set or <code>-1</code>
 * @since 3.0
 */
protected void enabledRedrawing(int topIndex) {
  if (fDocumentAdapter instanceof IDocumentAdapterExtension) {
    IDocumentAdapterExtension extension= (IDocumentAdapterExtension) fDocumentAdapter;
    StyledText textWidget= getTextWidget();
    if (textWidget != null && !textWidget.isDisposed()) {
      extension.resumeForwardingDocumentChanges();
      if (topIndex > -1) {
        try {
          setTopIndex(topIndex);
        } catch (IllegalArgumentException x) {
          // changes don't allow for the previous top pixel
        }
      }
    }
  }
  if (fViewerState != null) {
    fViewerState.restore(topIndex == -1);
    fViewerState= null;
  }
  if (fTextWidget != null && !fTextWidget.isDisposed())
    fTextWidget.setRedraw(true);
  fireRedrawChanged();
}