Progress Bar
Progress Bar shows the completion status of a task or process. The progress can be determinate or indeterminate. Use Progress Bar to show an ongoing process that takes a noticeable time to finish.
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ProgressBar progressBar = new ProgressBar();
progressBar.setValue(0.5);
add(progressBar);|
Note
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Global loading indicator
A global loading indicator shows at the top of the viewport while processing a server request, after a configurable delay.
You do not need to provide an explicit Progress Bar for these situations.
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Modes
Determinate
Use a determinate Progress Bar when progress can be computed.
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ProgressBar progressBar = new ProgressBar();
progressBar.setValue(0.5);
Div progressBarLabel = new Div();
progressBarLabel.setText("Processing Financials.xlsx (50%)");
add(progressBarLabel, progressBar);Indeterminate
Use an indeterminate Progress Bar to show that progress is ongoing but cannot be computed.
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ProgressBar progressBar = new ProgressBar();
progressBar.setIndeterminate(true);
Div progressBarLabel = new Div();
progressBarLabel.setText("Generating report...");
add(progressBarLabel, progressBar);Bounds and Initial Value
The progress value defaults to a range from 0 to 1, with an initial value of 0. These can be changed to any numeric values:
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ProgressBar progressBar = new ProgressBar();
progressBar.setMin(0);
progressBar.setMax(100);
progressBar.setValue(50);
Div progressBarLabel = new Div();
progressBarLabel.setText("Processing files (50/100)");
add(progressBarLabel, progressBar);Theme Variants
Progress Bar comes with three theme variants: contrast, success and error.
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ProgressBar progressBarContrast = new ProgressBar();
progressBarContrast.addThemeVariants(ProgressBarVariant.LUMO_CONTRAST);| Variant | Theme name | Usage recommendations |
|---|---|---|
Success | success | * When progress is satisfactory and/or nearing completion * Visual preference |
Error | error | * When progress is unsatisfactory * Draw the user’s attention to a stalled or failed process |
Contrast | contrast | * Visual preference |
Best Practices
Provide a Label
Use labels to give context to a Progress Bar. Labels can also show the progress of a determinate progress bar in text in addition to graphical representation, for example, completion percentage or number of items processed.
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ProgressBar progressBar = new ProgressBar();
progressBar.setValue(0.5);
Div progressBarLabelText = new Div();
progressBarLabelText.setText("Processing Financials.xlsx");
Div progressBarLabelValue = new Div();
progressBarLabelValue.setText("50%");
FlexLayout progressBarLabel = new FlexLayout();
progressBarLabel.setJustifyContentMode(JustifyContentMode.BETWEEN);
progressBarLabel.add(progressBarLabelText, progressBarLabelValue);
add(progressBarLabel, progressBar);State Switching
Switch from indeterminate to determinate if the progress becomes computable, and vice versa.
Estimate Completion Time
Provide estimates when possible. If a process takes approximately 20 minutes communicate that to the user.
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ProgressBar progressBar = new ProgressBar();
progressBar.setIndeterminate(true);
Div progressBarLabel = new Div();
progressBarLabel.setText("Generating report, please wait...");
Div progressBarSubLabel = new Div();
progressBarSubLabel.getStyle().set("font-size", "var(--lumo-font-size-xs)");
progressBarSubLabel.setText("Process can take upwards of 10 minutes");
add(progressBarLabel, progressBar, progressBarSubLabel);Asynchronous Processes
If the user is waiting for a process to finish use, consider using a Notification to notify them upon its completion and/or failure. This is useful if the processing takes place “off-screen” or the user is doing other work while waiting.
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Note
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Avoid blocking processes
Use asynchronous processes whenever possible so as not to block the user from completing other tasks while waiting for the process to finish.
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When to Use
If a back-end process takes longer than 1 second, use a Progress Bar to show to the user that something is happening, especially if it blocks the user’s workflow.
Placement
A Progress Bar’s location in the UI indicates to the user its scope and whether the surrounding UI is operable during its progression.
For example, a Vaadin application’s built-in loading indicator is placed at the top of the viewport to show that it affects the entire application. The UI is generally not operable during pending server requests.
Placing a Progress Bar in a dialog, details panel or an otherwise defined section, indicates that the process displayed is specific to that section. Depending on the user case, the user may or may not be able to interact with the UI.