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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