UI组件-ProgressIndicator组件
ProgressIndicator 组件显示进程条，ProgressIndicator 组件定时向服务器查询其当前值，如果值有变化，则更新进程条进度。Web 应用本身无需实现任何查询服务器的操作，查询由ProgressIndicator 组件自动完成。 ProgressIndicator 组件的值域为0.0到1.0之间。缺省的查询(polling)间隔为1秒，可以使用setPollingInterval 修改。
// Create the indicator
final ProgressIndicator indicator =
new ProgressIndicator(new Float(0.0));
main.addComponent(indicator);
// Set polling frequency to 0.5 seconds.
indicator.setPollingInterval(500);
ProgressIndicator 组件通常用来显示一些耗时操作（比如下载文件）的进度。 使用 setValue 为ProgressIndicator 组件设置当前值。 下面代码模拟一个费时操作提供 ProgressIndicator 组件显示进度。
// Create an indicator that makes you look busy
final ProgressIndicator indicator =
new ProgressIndicator(new Float(0.0));
main.addComponent(indicator);
// Set polling frequency to 0.5 seconds.
indicator.setPollingInterval(500);
// Add a button to start working
final Button button = new Button("Click to start");
main.addComponent(button);
// Another thread to do some work
class WorkThread extends Thread {
public void run () {
double current = 0.0;
while (true) {
// Do some "heavy work"
try {
sleep(50); // Sleep for 50 milliseconds
} catch (InterruptedException e) {}
// Show that you have made some progress:
// grow the progress value until it reaches 1.0.
current += 0.01;
if (current>1.0)
indicator.setValue(new Float(1.0));
else
indicator.setValue(new Float(current));
// After all the "work" has been done for a while,
// take a break.
if (current > 1.2) {
// Restore the state to initial.
indicator.setValue(new Float(0.0));
button.setVisible(true);
break;
}
}
}
}
// Clicking the button creates and runs a work thread
button.addListener(new Button.ClickListener() {
public void buttonClick(ClickEvent event) {
final WorkThread thread = new WorkThread();
thread.start();
// The button hides until the work is done.
button.setVisible(false);
}
});
