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+---
+title: ProgressBar
+order: 27
+layout: page
+---
+
+[[components.progressbar]]
+= [classname]#ProgressBar#
+
+The [classname]#ProgressBar# component allows displaying the progress of a task
+graphically. The progress is specified as a floating-point value between 0.0 and
+1.0.
+
+[[figure.components.progressbar.basic]]
+.The Progress Bar Component
+image::img/progressbar-basic.png[]
+
+To display upload progress with the [classname]#Upload# component, you can
+update the progress bar in a [interfacename]#ProgressListener#.
+
+When the position of a progress bar is done in a background thread, the change
+is not shown in the browser immediately. You need to use either polling or
+server push to update the browser. You can enable polling with
+[methodname]#setPollInterval()# in the current UI instance. See
+<<dummy/../../../framework/advanced/advanced-push#advanced.push,"Server Push">>
+for instructions about using server push. Whichever method you use to update the
+UI, it is important to lock the user session by modifying the progress bar value
+inside [methodname]#access()# call, as illustrated in the following example and
+described in
+<<dummy/../../../framework/advanced/advanced-push#advanced.push.running,"Accessing
+UI from Another Thread">>.
+
+
+[source, java]
+----
+final ProgressBar bar = new ProgressBar(0.0f);
+layout.addComponent(bar);
+        
+layout.addComponent(new Button("Increase",
+    new ClickListener() {
+    @Override
+    public void buttonClick(ClickEvent event) {
+        float current = bar.getValue();
+        if (current < 1.0f)
+            bar.setValue(current + 0.10f);
+    }
+}));
+----
+
+[[components.progressbar.indeterminate]]
+== Indeterminate Mode
+
+In the indeterminate mode, a non-progressive indicator is displayed
+continuously. The indeterminate indicator is a circular wheel in the built-in
+themes. The progress value has no meaning in the indeterminate mode.
+
+
+[source, java]
+----
+ProgressBar bar = new ProgressBar();
+bar.setIndeterminate(true);
+----
+
+[[figure.components.progressbar.indeterminate]]
+.Indeterminate Progress Bar
+image::img/progressbar-indeterminate.png[]
+
+
+ifdef::web[]
+[[components.progressbar.thread]]
+== Doing Heavy Computation
+
+The progress indicator is often used to display the progress of a heavy
+server-side computation task, often running in a background thread. The UI,
+including the progress bar, can be updated either with polling or by using
+server push. When doing so, you must ensure thread-safety, most easily by
+updating the UI inside a [methodname]#UI.access()# call in a
+[interfacename]#Runnable#, as described in
+<<dummy/../../../framework/advanced/advanced-push#advanced.push.running,"Accessing
+UI from Another Thread">>.
+
+In the following example, we create a thread in the server to do some "heavy
+work" and use polling to update the UI. All the thread needs to do is to set the
+value of the progress bar with [methodname]#setValue()# and the current progress
+is displayed automatically when the browser polls the server.
+
+
+[source, java]
+----
+HorizontalLayout barbar = new HorizontalLayout();
+layout.addComponent(barbar);
+        
+// Create the indicator, disabled until progress is started
+final ProgressBar progress = new ProgressBar(new Float(0.0));
+progress.setEnabled(false);
+barbar.addComponent(progress);
+        
+final Label status = new Label("not running");
+barbar.addComponent(status);
+
+// A button to start progress
+final Button button = new Button("Click to start");
+layout.addComponent(button);
+
+// A thread to do some work
+class WorkThread extends Thread {
+    // Volatile because read in another thread in access()
+    volatile double current = 0.0;
+
+    @Override
+    public void run() {
+        // Count up until 1.0 is reached
+        while (current < 1.0) {
+            current += 0.01;
+
+            // Do some "heavy work"
+            try {
+                sleep(50); // Sleep for 50 milliseconds
+            } catch (InterruptedException e) {}
+
+            // Update the UI thread-safely
+            UI.getCurrent().access(new Runnable() {
+                @Override
+                public void run() {
+                    progress.setValue(new Float(current));
+                    if (current < 1.0)
+                        status.setValue("" +
+                            ((int)(current*100)) + "% done");
+                    else
+                        status.setValue("all done");
+                }
+            });
+        }
+        
+        // Show the "all done" for a while
+        try {
+            sleep(2000); // Sleep for 2 seconds
+        } catch (InterruptedException e) {}
+
+        // Update the UI thread-safely
+        UI.getCurrent().access(new Runnable() {
+            @Override
+            public void run() {
+                // Restore the state to initial
+                progress.setValue(new Float(0.0));
+                progress.setEnabled(false);
+                        
+                // Stop polling
+                UI.getCurrent().setPollInterval(-1);
+                
+                button.setEnabled(true);
+                status.setValue("not running");
+            }
+        });
+    }
+}
+
+// Clicking the button creates and runs a work thread
+button.addClickListener(new Button.ClickListener() {
+    public void buttonClick(ClickEvent event) {
+        final WorkThread thread = new WorkThread();
+        thread.start();
+
+        // Enable polling and set frequency to 0.5 seconds
+        UI.getCurrent().setPollInterval(500);
+
+        // Disable the button until the work is done
+        progress.setEnabled(true);
+        button.setEnabled(false);
+
+        status.setValue("running...");
+    }
+});
+----
+
+The example is illustrated in <<figure.components.progressbar.thread>>.
+
+[[figure.components.progressbar.thread]]
+.Doing Heavy Work
+image::img/progressbar-thread.png[]
+
+endif::web[]
+
+[[components.progressbar.css]]
+== CSS Style Rules
+
+
+[source, css]
+----
+.v-progressbar, v-progressbar-indeterminate {}
+  .v-progressbar-wrapper {}
+    .v-progressbar-indicator {}
+----
+
+The progress bar has a [literal]#++v-progressbar++# base style. The animation is
+the background of the element with [literal]#++v-progressbar-wrapper++# style,
+by default an animated GIF image. The progress is an element with
+[literal]#++v-progressbar-indicator++# style inside the wrapper, and therefore
+displayed on top of it. When the progress element grows, it covers more and more
+of the animated background.
+
+In the indeterminate mode, the top element also has the
+[literal]#++v-progressbar-indeterminate++# style. The built-in themes simply
+display the animated GIF in the top element and have the inner elements
+disabled.
+
+
+
+