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Progress Bar

Source: TypeScript / Java
Progress Bar shows the amount of completion of a task or process.

Progress Bar shows the amount of completion 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
Global loading indicator
A global loading indicator shows at the top of the viewport while processing a server request, after a configurable delay. You don’t need to provide an explicit Progress Bar for these situations.

Modes

Determinate

Use a determinate Progress Bar when progress can be computed.

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ProgressBar progressBar = new ProgressBar();
progressBar.setValue(0.5);

Indeterminate

Use an indeterminate Progress Bar to show that progress is ongoing but can’t be computed.

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ProgressBar progressBar = new ProgressBar();
progressBar.setIndeterminate(true);

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);

Theme Variants

Progress Bar comes with three theme variants: contrast, success, and error.

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// Contrast
ProgressBar progressBarContrast = new ProgressBar();
progressBarContrast.addThemeVariants(ProgressBarVariant.LUMO_CONTRAST);
progressBarContrast.setValue(0.5);

// Success
ProgressBar progressBarSuccess = new ProgressBar();
progressBarSuccess.addThemeVariants(ProgressBarVariant.LUMO_SUCCESS);
progressBarSuccess.setValue(0.75);

// Error
ProgressBar progressBarError = new ProgressBar();
progressBarError.addThemeVariants(ProgressBarVariant.LUMO_ERROR);
progressBarError.setValue(0.2);
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 a graphical representation, for example the percentage of completion, or the number of items processed.

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ProgressBar progressBar = new ProgressBar();
progressBar.setValue(0.5);

NativeLabel progressBarLabelText = new NativeLabel(
        "Processing Financials.xlsx");
progressBarLabelText.setId("pblabel");
// Associates the label with the progressbar for screen readers:
progressBar.getElement().setAttribute("aria-labelledby", "pblabel");

Span progressBarLabelValue = new Span("50%");
HorizontalLayout progressBarLabel = new HorizontalLayout(
        progressBarLabelText, progressBarLabelValue);
progressBarLabel.setJustifyContentMode(JustifyContentMode.BETWEEN);

add(progressBarLabel, progressBar);

State Switching

Switch from indeterminate to determinate if the progress becomes computable, and similarly from determinate to indeterminate if it becomes non-computable.

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);

NativeLabel progressBarLabel = new NativeLabel("Generating report...");
progressBarLabel.setId("pblbl");
progressBarLabel.addClassName(LumoUtility.TextColor.SECONDARY);

Span progressBarSubLabel = new Span(
        "Process can take upwards of 10 minutes");
progressBarSubLabel.setId("sublbl");
progressBarSubLabel.addClassNames(LumoUtility.TextColor.SECONDARY,
        LumoUtility.FontSize.XSMALL);

// Associates the labels with the bar programmatically, for screen
// readers:
progressBar.getElement().setAttribute("aria-labelledby", "pblbl");
progressBar.getElement().setAttribute("aria-describedby", "sublbl");

add(progressBarLabel, progressBar, progressBarSubLabel);

Asynchronous Processes

If the user is waiting for a process to finish, 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.

Note
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.

When to Use

If a backend process takes longer than 1 second, use a Progress Bar to show the user that something is happening, especially if it blocks the user’s workflow.

Placement

A Progress Bar’s location in the UI implies 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 not operable during pending server requests.

Placing a Progress Bar in a dialog, details panel or an otherwise defined section implies that the process displayed is specific to that section. Depending on the use case, the user may or may not be able to interact with the UI.

Component Usage recommendations

Upload

Component for uploading files.

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