GWT image get from server - gwt

Question

when I implemented as given here but for not working
my implementation is
ServerSide:
File f = fileFromDatabase // from database the fileName is india.png
DataInputStream din = new DataInputStream(new FileInputStream(f));
din.readFully(data);
din.close();
String base64 = Base64Utils.toBase64(data);
String[] s = filename.split("\\.");
base64 = "data:" + "india/png" + ";base64," + base64;
or
base64 = "data:image/png;base64," + base64;
return base64;
clientSide:
imageService.getImageData(new AsyncCallback() {
#Override
public void onSuccess(String imageData) {
Image image = new Image(imageData);
Canvas.addChild(image);
//this Canvas class addItem into com.smartgwt.client.widgets.Window
}
#Override
public void onFailure(Throwable caught) {
}
}
client side imageData stirng is <image class="gwt-Image src=sume big string starts with "data:image/png;base64,someSting......>"
eventhough client side could not see the image.
Please clear my doubt
Thanks in advance

Answer 1

When you get the base64 string from the server you need to add a load handler on the image in the DOM. The way I've done it is to attach it to the DOM and hide it as in the below code.
/** get events preview from server, attach to the DOM and store in 'preview'
* #param handler option to pass a custom load handler
*/
private void get_preview(LoadHandler handler) {
final LoadHandler load_handler = handler;
server.getPreviewImage(user, data, new AsyncCallback<String>() {
#Override
public void onFailure(Throwable caught) {
log.info("getPreviewImage: " + error);
}
#Override
public void onSuccess(String result) {
preview = null;
if (result != null) {
ImageElement ie = doc.createImageElement();
preview = Image.wrap(ie);
preview.setVisible(false);
doc.getElementById("imagedummy").removeAllChildren();
doc.getElementById("imagedummy").appendChild(preview.getElement());
// add load handler to DOM image before being able to use
if (load_handler == null) {
preview.addLoadHandler(new LoadHandler() {
#Override
public void onLoad(LoadEvent event) {
display_preview();
}
});
} else {
preview.addLoadHandler(load_handler);
}
preview.setUrl(result);
}
}
});
}
/** Displays the preview on the canvas.
* Resizes canvas if necessary and sets zoom
*/
private void display_preview() {
EventSize size = data.getEventSize();
canvas.canvas.setCoordinateSpaceWidth(size.width);
canvas.canvas.setCoordinateSpaceHeight(size.height);
float zoom = Float.parseFloat(preview_zoom.getSelectedValue());
canvas.canvas.setPixelSize((int)(size.width * zoom), (int)(size.height * zoom));
if (preview != null) {
ImageElement elem = ImageElement.as(preview.getElement());
canvas.canvas.getContext2d().drawImage(elem, 0, 0);
}
}