Re: re-drawing visualizations in GWT

Hello there,

I have the exactly same question. Did you find out the solution?

Thanks

Aaron

On Wednesday, August 18, 2010 6:40:21 AM UTC+8, Jawfish wrote:

This should be a simple question, but I have read many pages of the
Docs and examples and can't find it....

Me:
Java and Javascript beginner.

Intent:
I am making a small demo app in GWT 2.0x with charts. It intends to
put up a chart and then redraws the chart with new data.

Problem:
Nothing happens when I use the draw method on the chart object. It
seems that once drawn the chart object is rendered in JS, and I can't
talk to it again. I haven't found docs, or maybe haven't understood
the dynamic relationship between the Java GWT code and the JS code
running in the browser. Almost all examples for charts are in JS. I
see the Gauge visualization re-drawing itself in the example, but no
Java source code.

Thanks.
John

My code:

package com.demo.gwtdemoviz1.client;


import com.google.gwt.core.client.JavaScriptObject;
import com.google.gwt.core.client.JavaScriptException;


import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.core.client.JsArray;
import com.google.gwt.user.client.Random;
import com.google.gwt.user.client.Timer;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.Panel;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.visualization.client.AbstractDataTable;
import com.google.gwt.visualization.client.DataView;
import com.google.gwt.visualization.client.Query;
import com.google.gwt.visualization.client.QueryResponse;
import com.google.gwt.visualization.client.VisualizationUtils;
import com.google.gwt.visualization.client.DataTable;
import com.google.gwt.visualization.client.Selection;
import
com.google.gwt.visualization.client.AbstractDataTable.ColumnType;
import com.google.gwt.visualization.client.Query.Callback;
import com.google.gwt.visualization.client.events.SelectHandler;
import com.google.gwt.visualization.client.visualizations.BarChart;
import
com.google.gwt.visualization.client.visualizations.Visualization;
import
com.google.gwt.visualization.client.visualizations.BarChart.Options;

public class GWTDemoViz1 implements EntryPoint {

        // stuff to randomize the data
         private static final int REFRESH_INTERVAL = 5000; // ms
        // randomize the variables
        private void randomData(Visualization<Options> bar) {
                // do something here to change data

/////////////////////////////// this is where it
fails //////////////////////////////////////
                bar.draw( updateTable() );
// updateTable() is called and it runs, the changed values can be
seen
// in the browser; further it can instantiate a fresh barchart if I
swap it for
// createTable(), but used as a refresh, the chart never redraws.
///////////////////////////////////////////////////////////////////////////////////////////////////////
        }


  public void onModuleLoad() {
    // Create a callback to be called when the visualization API
    // has been loaded.
            Runnable onLoadCallback = new Runnable() {
              public void run() {
                Panel panel = RootPanel.get();

                // Create a pie chart visualization.
                BarChart bar = new BarChart(createTable(), createOptions());

                bar.addSelectHandler(createSelectHandler(bar));
                panel.add(bar);

              }

            };
    // Setup timer to refresh data automatically.
    Timer refreshTimer = new Timer() {
      @Override
                      public void run() {
                        randomData(null);
                      }
     };
    refreshTimer.scheduleRepeating( REFRESH_INTERVAL );

    // Load the visualization api, passing the onLoadCallback to be
called
    // when loading is done.
    VisualizationUtils.loadVisualizationApi(onLoadCallback,
BarChart.PACKAGE);
  }

  private Options createOptions() {
    Options options = Options.create();
    options.setWidth(400);
    options.setHeight(240);
    options.set3D(true);
    options.setTitle("My Daily Activities");
    return options;
  }

  private SelectHandler createSelectHandler(final BarChart bar) {
    */... just the selecthandler from the simpleviz demo .... */
          }
        }

        Window.alert(message);
      }
    };
  }

  private AbstractDataTable createTable() {
            // Underlying data
            DataTable data = DataTable.create();
            data.addColumn(ColumnType.STRING, "Item");
            data.addColumn(ColumnType.NUMBER, "item per sec");
            data.addRows(3);
            data.setValue(0, 0, "Nits");
            data.setValue(0, 1, 10);
            data.setValue(1, 0, "Gnats");
            data.setValue(1, 1, 4);
            data.setValue(2, 0, "Pits");
            data.setValue(2, 1, 8);

            // Data view -- read only, and no location column
            DataView result = DataView.create(data);
            result.setColumns(new int[]{0, 1});
            return result;

          }

  private AbstractDataTable updateTable() {
            // Underlying data
            DataTable data = DataTable.create();
            data.addColumn(ColumnType.STRING, "Item");
            data.addColumn(ColumnType.NUMBER, "item per sec");

            // now create some values
            String message = "";
            final int MAX_VALUE = 10;
            int nit = Random.nextInt(MAX_VALUE) ;
            int gnat = Random.nextInt(MAX_VALUE) ;
            int pit = Random.nextInt(MAX_VALUE) ;

            data.addRows(3);
            data.setValue(0, 0, "Nits");
            data.setValue(0, 1, nit);
            data.setValue(1, 0, "Gnats");
            data.setValue(1, 1, gnat);
            data.setValue(2, 0, "Pits");
            data.setValue(2, 1, pit);
            message +=  nit + " valu " + nit + " other " + gnat;
//Window.alert(message);

            return data;

          }

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