我发现了这个来自Oracle网站的测试项目,因为我想在我的项目中添加一个圆形进度条。
我正在使用Netbeans开发应用程序,但当我启动应用程序时,应该有圆形进度条的JPanel却消失了。
我已经删除了所有与解决此问题无关的代码,并得到了以下代码:
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import javax.swing.*;
import javax.swing.plaf.LayerUI;
public class Loading_Test extends javax.swing.JFrame
{
static final WaitLayerUI layerUI = new WaitLayerUI();
public Loading_Test()
{
JPanel panel = new JPanel();
JLayer<JPanel> jlayer = new JLayer<>(panel, layerUI);
add(jlayer);
initComponents();
}
@SuppressWarnings("unchecked")
private void initComponents() {
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 400, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 300, Short.MAX_VALUE)
);
pack();
}
public static void main(String args[])
{
java.awt.EventQueue.invokeLater(new Runnable()
{
@Override
public void run()
{
JFrame frame = new Loading_Test();
frame.setVisible(true);
layerUI.start();
}
});
}
}
class WaitLayerUI extends LayerUI<JPanel> implements ActionListener
{
private boolean mIsRunning;
private boolean mIsFadingOut;
private Timer mTimer;
private int mAngle;
private int mFadeCount;
private int mFadeLimit = 15;
@Override
public void paint(Graphics g, JComponent c)
{
int w = c.getWidth();
int h = c.getHeight();
// Paint the view.
super.paint(g, c);
if (!mIsRunning)
{
return;
}
Graphics2D g2 = (Graphics2D) g.create();
float fade = (float) mFadeCount / (float) mFadeLimit;
// Gray it out.
Composite urComposite = g2.getComposite();
g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, .5f * fade));
g2.fillRect(0, 0, w, h);
g2.setComposite(urComposite);
// Paint the wait indicator.
int s = Math.min(w, h) / 5;
int cx = w / 2;
int cy = h / 2;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(new BasicStroke(s / 4, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND));
g2.setPaint(Color.white);
g2.rotate(Math.PI * mAngle / 180, cx, cy);
for (int i = 0; i < 12; i++)
{
float scale = (11.0f - (float) i) / 11.0f;
g2.drawLine(cx + s, cy, cx + s * 2, cy);
g2.rotate(-Math.PI / 6, cx, cy);
g2.setComposite(AlphaComposite.getInstance(
AlphaComposite.SRC_OVER, scale * fade));
}
g2.dispose();
}
@Override
public void actionPerformed(ActionEvent e)
{
if (mIsRunning)
{
firePropertyChange("tick", 0, 1);
mAngle += 3;
if (mAngle >= 360)
{
mAngle = 0;
}
if (mIsFadingOut)
{
if (--mFadeCount == 0)
{
mIsRunning = false;
mTimer.stop();
}
}
else if (mFadeCount < mFadeLimit)
{
mFadeCount++;
}
}
}
public void start()
{
if (mIsRunning)
{
return;
}
// Run a thread for animation.
mIsRunning = true;
mIsFadingOut = false;
mFadeCount = 0;
int fps = 24;
int tick = 1000 / fps;
mTimer = new Timer(tick, this);
mTimer.start();
}
public void stop()
{
mIsFadingOut = true;
}
@Override
public void applyPropertyChange(PropertyChangeEvent pce, JLayer l)
{
if ("tick".equals(pce.getPropertyName()))
{
l.repaint();
}
}
}
如果您按照当前代码运行,您会遇到和我一样的问题,JPanel未被显示。但是,我发现如果我删除与布局相关的代码(27~36行),进度条就可以工作了。您还需要手动设置窗口大小。
setSize(300, 300);
之后
pack();
由于布局行是由Netbeans自动生成的,因此我正在尝试理解如何解决此问题,因为这些特定的代码行被Netbeans编辑器阻止编辑。
initComponents
调用和add(jlayer)
调用吗?如果你在initComponents
中的调用与你已经添加到框架中的JLayer
产生冲突,那我不会感到惊讶。 - RobingetContentPane().setLayout(layout);
这行代码有问题。如果我注释掉它,就可以显示加载了。 - Deviling Master