blocks|key|1738214|text|这应该适用于所有版本的Java|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1738215|public+static+void+centreWindow(Window+frame)+{
++++Dimension+dimension+=+Toolkit.getDefaultToolkit().getScreenSize();
++++int+x+=+(int)+((dimension.getWidth()+-+frame.getWidth())+/+2);
++++int+y+=+(int)+((dimension.getHeight()+-+frame.getHeight())+/+2);
++++frame.setLocation(x,+y);
}|code-block|syntax|javascript|1738216|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This should work in all versions of Java

<pre><code>public static void centreWindow(Window frame) {
 Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
 int x = (int) ((dimension.getWidth() - frame.getWidth()) / 2);
 int y = (int) ((dimension.getHeight() - frame.getHeight()) / 2);
 frame.setLocation(x, y);
}
</code></pre>

blocks|key|1738404|text|应该在使用setSize(x,y)或pack()之后调用setLocationRelativeTo(null)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1738405|entityMap^0|5|C|I|6|S|R|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

<code>setLocationRelativeTo(null)</code> should be called after you either use <code>setSize(x,y)</code>, or use <code>pack()</code>.

blocks|key|1523267|text|请注意，setLocationRelativeTo(null)和Tookit.getDefaultToolkit().getScreenSize()技术仅适用于主监视器。如果您处于多监视器环境中，则在执行此类计算之前，可能需要获取有关窗口所在特定监视器的信息。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1523268|有时重要，有时不重要..。|1523269|有关如何获得此功能的更多信息，请参阅GraphicsEnvironment+javadocs。|offset|length|1523270|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/7/docs/api/java/awt/GraphicsEnvironment.html^0|0|0|I|S|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@$F|S|G|T|1|U]]|A|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]]]

Note that both the setLocationRelativeTo(null) and Tookit.getDefaultToolkit().getScreenSize() techniques work only for the primary monitor. If you are in a multi-monitor environment, you may need to get information about the specific monitor the window is on before doing this kind of calculation.

Sometimes important, sometimes not...

See <a href="https://docs.oracle.com/javase/7/docs/api/java/awt/GraphicsEnvironment.html" rel="nofollow noreferrer">GraphicsEnvironment javadocs</a> for more info on how to get this.

blocks|key|1523439|text|在Linux上，代码|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1523440|setLocationRelativeTo(null)|code-block|syntax|javascript|1523441|在多显示器环境中，每次启动窗口时，都会将窗口放在随机位置。和代码|1523442|setLocation((Toolkit.getDefaultToolkit().getScreenSize().width++-+getSize().width)+/+2,+(Toolkit.getDefaultToolkit().getScreenSize().height+-+getSize().height)+/+2);|1523443|将窗口“切成两半”，把它放在我的两个显示器之间的中心位置。我使用以下方法将其居中：|1523444|private+void+setWindowPosition(JFrame+window,+int+screen)
{++++++++
++++GraphicsEnvironment+env+=+GraphicsEnvironment.getLocalGraphicsEnvironment();
++++GraphicsDevice[]+allDevices+=+env.getScreenDevices();
++++int+topLeftX,+topLeftY,+screenX,+screenY,+windowPosX,+windowPosY;

++++if+(screen+<+allDevices.length+&&+screen+>+-1)
++++{
++++++++topLeftX+=+allDevices[screen].getDefaultConfiguration().getBounds().x;
++++++++topLeftY+=+allDevices[screen].getDefaultConfiguration().getBounds().y;

++++++++screenX++=+allDevices[screen].getDefaultConfiguration().getBounds().width;
++++++++screenY++=+allDevices[screen].getDefaultConfiguration().getBounds().height;
++++}
++++else
++++{
++++++++topLeftX+=+allDevices[0].getDefaultConfiguration().getBounds().x;
++++++++topLeftY+=+allDevices[0].getDefaultConfiguration().getBounds().y;

++++++++screenX++=+allDevices[0].getDefaultConfiguration().getBounds().width;
++++++++screenY++=+allDevices[0].getDefaultConfiguration().getBounds().height;
++++}

++++windowPosX+=+((screenX+-+window.getWidth())++/+2)+%2B+topLeftX;
++++windowPosY+=+((screenY+-+window.getHeight())+/+2)+%2B+topLeftY;

++++window.setLocation(windowPosX,+windowPosY);
}|1523445|使窗口正好显示在第一个显示的中心。这可能不是最简单的解决方案。|1523446|在Linux、Windows和Mac上工作正常。|1523447|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|11|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

On Linux the code

<pre class="lang-java prettyprint-override"><code>setLocationRelativeTo(null)
</code></pre>

Put my window to random location each time I launched it, in a multi display environment.
And the code

<pre class="lang-java prettyprint-override"><code>setLocation((Toolkit.getDefaultToolkit().getScreenSize().width - getSize().width) / 2, (Toolkit.getDefaultToolkit().getScreenSize().height - getSize().height) / 2);
</code></pre>

"cut" the window in half with placing it to the exact center, which is between my two displays.
I used the following method to center it:

<pre><code>private void setWindowPosition(JFrame window, int screen)
{ 
 GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
 GraphicsDevice[] allDevices = env.getScreenDevices();
 int topLeftX, topLeftY, screenX, screenY, windowPosX, windowPosY;

 if (screen &lt; allDevices.length &amp;&amp; screen &gt; -1)
 {
 topLeftX = allDevices[screen].getDefaultConfiguration().getBounds().x;
 topLeftY = allDevices[screen].getDefaultConfiguration().getBounds().y;

 screenX = allDevices[screen].getDefaultConfiguration().getBounds().width;
 screenY = allDevices[screen].getDefaultConfiguration().getBounds().height;
 }
 else
 {
 topLeftX = allDevices[0].getDefaultConfiguration().getBounds().x;
 topLeftY = allDevices[0].getDefaultConfiguration().getBounds().y;

 screenX = allDevices[0].getDefaultConfiguration().getBounds().width;
 screenY = allDevices[0].getDefaultConfiguration().getBounds().height;
 }

 windowPosX = ((screenX - window.getWidth()) / 2) + topLeftX;
 windowPosY = ((screenY - window.getHeight()) / 2) + topLeftY;

 window.setLocation(windowPosX, windowPosY);
}
</code></pre>

Makes the window appear right at the center of the first display.
This is probably not the easiest solution.

Works properly on Linux, Windows and Mac.

blocks|key|1523535|text|为了将主jFrame置于中心位置，我最终使用Swing+GUI表单在NetBeans中运行了这组代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1523536|package+my.SampleUIdemo;
import+java.awt.*;

public+class+classSampleUIdemo+extends+javax.swing.JFrame+{
++++///+
++++public+classSampleUIdemo()+{
++++++++initComponents();
++++++++CenteredFrame(this);++//+<---+Here+ya+go.
++++}
++++//+...
++++//+void+main()+and+other+public+method+declarations+here...

++++///++modular+approach
++++public+void+CenteredFrame(javax.swing.JFrame+objFrame){
++++++++Dimension+objDimension+=+Toolkit.getDefaultToolkit().getScreenSize();
++++++++int+iCoordX+=+(objDimension.width+-+objFrame.getWidth())+/+2;
++++++++int+iCoordY+=+(objDimension.height+-+objFrame.getHeight())+/+2;
++++++++objFrame.setLocation(iCoordX,+iCoordY);+
++++}+

}|code-block|syntax|javascript|1523537|或|1523538|package+my.SampleUIdemo;
import+java.awt.*;

public+class+classSampleUIdemo+extends+javax.swing.JFrame+{
++++++++///+
++++++++public+classSampleUIdemo()+{
++++++++++++initComponents();+
++++++++++++//------>>+Insert+your+code+here+to+center+main+jFrame.
++++++++++++Dimension+objDimension+=+Toolkit.getDefaultToolkit().getScreenSize();
++++++++++++int+iCoordX+=+(objDimension.width+-+this.getWidth())+/+2;
++++++++++++int+iCoordY+=+(objDimension.height+-+this.getHeight())+/+2;
++++++++++++this.setLocation(iCoordX,+iCoordY);+
++++++++++++//------>>+
++++++++}+
++++++++//+...
++++++++//+void+main()+and+other+public+method+declarations+here...

}|1523539|1523540|++++package+my.SampleUIdemo;
++++import+java.awt.*;
++++public+class+classSampleUIdemo+extends+javax.swing.JFrame+{
+++++++++///+
+++++++++public+classSampleUIdemo()+{
+++++++++++++initComponents();
+++++++++++++this.setLocationRelativeTo(null);++//+<<---+plain+and+simple
+++++++++}
+++++++++//+...
+++++++++//+void+main()+and+other+public+method+declarations+here...
+++}|1523541|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Q|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|R|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|K|3|H|5|6|7|T|8|@]|9|@]|A|$]]|$1|L|3|M|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|N|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|O|$]]

I finally got this bunch of codes to work in NetBeans using Swing GUI Forms in order to center main jFrame:

<pre><code>package my.SampleUIdemo;
import java.awt.*;

public class classSampleUIdemo extends javax.swing.JFrame {
 /// 
 public classSampleUIdemo() {
 initComponents();
 CenteredFrame(this); // &lt;--- Here ya go.
 }
 // ...
 // void main() and other public method declarations here...

 /// modular approach
 public void CenteredFrame(javax.swing.JFrame objFrame){
 Dimension objDimension = Toolkit.getDefaultToolkit().getScreenSize();
 int iCoordX = (objDimension.width - objFrame.getWidth()) / 2;
 int iCoordY = (objDimension.height - objFrame.getHeight()) / 2;
 objFrame.setLocation(iCoordX, iCoordY); 
 } 

}
</code></pre>

OR

<pre><code>package my.SampleUIdemo;
import java.awt.*;

public class classSampleUIdemo extends javax.swing.JFrame {
 /// 
 public classSampleUIdemo() {
 initComponents(); 
 //------&gt;&gt; Insert your code here to center main jFrame.
 Dimension objDimension = Toolkit.getDefaultToolkit().getScreenSize();
 int iCoordX = (objDimension.width - this.getWidth()) / 2;
 int iCoordY = (objDimension.height - this.getHeight()) / 2;
 this.setLocation(iCoordX, iCoordY); 
 //------&gt;&gt; 
 } 
 // ...
 // void main() and other public method declarations here...

}
</code></pre>

OR 

<pre><code> package my.SampleUIdemo;
 import java.awt.*;
 public class classSampleUIdemo extends javax.swing.JFrame {
 /// 
 public classSampleUIdemo() {
 initComponents();
 this.setLocationRelativeTo(null); // &lt;&lt;--- plain and simple
 }
 // ...
 // void main() and other public method declarations here...
 }
</code></pre>

blocks|key|1523279|text|frame.setLocationRelativeTo(null)；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1523280|完整示例：|1523281|public+class+BorderLayoutPanel+{

++++private+JFrame+mainFrame;
++++private+JButton+btnLeft,+btnRight,+btnTop,+btnBottom,+btnCenter;

++++public+BorderLayoutPanel()+{
++++++++mainFrame+=+new+JFrame("Border+Layout+Example");
++++++++btnLeft+=+new+JButton("LEFT");
++++++++btnRight+=+new+JButton("RIGHT");
++++++++btnTop+=+new+JButton("TOP");
++++++++btnBottom+=+new+JButton("BOTTOM");
++++++++btnCenter+=+new+JButton("CENTER");
++++}

++++public+void+SetLayout()+{
++++++++mainFrame.add(btnTop,+BorderLayout.NORTH);
++++++++mainFrame.add(btnBottom,+BorderLayout.SOUTH);
++++++++mainFrame.add(btnLeft,+BorderLayout.EAST);
++++++++mainFrame.add(btnRight,+BorderLayout.WEST);
++++++++mainFrame.add(btnCenter,+BorderLayout.CENTER);
++++++++//++++++++mainFrame.setSize(200,+200);
++++++++//++++++++or
++++++++mainFrame.pack();
++++++++mainFrame.setVisible(true);

++++++++//take+up+the+default+look+and+feel+specified+by+windows+themes
++++++++mainFrame.setDefaultLookAndFeelDecorated(true);

++++++++//make+the+window+startup+position+be+centered
++++++++mainFrame.setLocationRelativeTo(null);

++++++++mainFrame.setDefaultCloseOperation(mainFrame.EXIT_ON_CLOSE);
++++}
}|code-block|syntax|javascript|1523282|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

frame.setLocationRelativeTo(null);

Full example:

<pre class="lang-java prettyprint-override"><code>public class BorderLayoutPanel {

 private JFrame mainFrame;
 private JButton btnLeft, btnRight, btnTop, btnBottom, btnCenter;

 public BorderLayoutPanel() {
 mainFrame = new JFrame("Border Layout Example");
 btnLeft = new JButton("LEFT");
 btnRight = new JButton("RIGHT");
 btnTop = new JButton("TOP");
 btnBottom = new JButton("BOTTOM");
 btnCenter = new JButton("CENTER");
 }

 public void SetLayout() {
 mainFrame.add(btnTop, BorderLayout.NORTH);
 mainFrame.add(btnBottom, BorderLayout.SOUTH);
 mainFrame.add(btnLeft, BorderLayout.EAST);
 mainFrame.add(btnRight, BorderLayout.WEST);
 mainFrame.add(btnCenter, BorderLayout.CENTER);
 // mainFrame.setSize(200, 200);
 // or
 mainFrame.pack();
 mainFrame.setVisible(true);

 //take up the default look and feel specified by windows themes
 mainFrame.setDefaultLookAndFeelDecorated(true);

 //make the window startup position be centered
 mainFrame.setLocationRelativeTo(null);

 mainFrame.setDefaultCloseOperation(mainFrame.EXIT_ON_CLOSE);
 }
}
</code></pre>

blocks|key|1523326|text|以下内容不适用于JDK+1.7.0.07：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1523327|frame.setLocationRelativeTo(null);|code-block|syntax|javascript|1523328|它将左上角放在中心-不同于居中窗口。另一个也不起作用，涉及到frame.getSize()和dimension.getSize()：|1523329|Dimension+dimension+=+Toolkit.getDefaultToolkit().getScreenSize();
int+x+=+(int)+((dimension.getWidth()+-+frame.getWidth())+/+2);
int+y+=+(int)+((dimension.getHeight()+-+frame.getHeight())+/+2);
frame.setLocation(x,+y);|1523330|getSize()方法继承自Component类，因此frame.getSize也返回窗口的大小。因此，从垂直和水平尺寸中减去垂直和水平尺寸的一半，以找到放置左上角的位置的x，y坐标，得到中心点的位置，这最终也会使窗口居中。然而，上面代码的第一行是有用的，"Dimension...“。只需将其置于中心位置即可：|1523331|Dimension+dimension+=+Toolkit.getDefaultToolkit().getScreenSize();
JLabel+emptyLabel+=+new+JLabel("");
emptyLabel.setPreferredSize(new+Dimension(+(int)dimension.getWidth()+/+2,+(int)dimension.getHeight()/2+));
frame.getContentPane().add(emptyLabel,+BorderLayout.CENTER);
frame.setLocation((int)dimension.getWidth()/4,+(int)dimension.getHeight()/4);|1523332|JLabel设置屏幕大小。它的FrameDemo.java版本可以在Oracle/Sun站点上的java教程中找到。我将其设置为屏幕高度/宽度的一半。然后，我将屏幕尺寸的1/4放在左上角，将屏幕尺寸的1/4放在左上角。您可以使用类似的概念。|1523333|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

The following doesn't work for JDK 1.7.0.07:

<pre><code>frame.setLocationRelativeTo(null);
</code></pre>

It puts the top left corner at the center - not the same as centering the window. The other one doesn't work either, involving frame.getSize() and dimension.getSize():

<pre><code>Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
int x = (int) ((dimension.getWidth() - frame.getWidth()) / 2);
int y = (int) ((dimension.getHeight() - frame.getHeight()) / 2);
frame.setLocation(x, y);
</code></pre>

The getSize() method is inherited from the Component class, and therefore frame.getSize returns the size of the window as well. Thus subtracting half the vertical and horizontal dimensions from the vertical and horizontal dimensions, to find the x,y coordinates of where to place the top-left corner, gives you the location of the center point, which ends up centering the window as well. However, the first line of the above code is useful, "Dimension...". Just do this to center it:

<pre><code>Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
JLabel emptyLabel = new JLabel("");
emptyLabel.setPreferredSize(new Dimension( (int)dimension.getWidth() / 2, (int)dimension.getHeight()/2 ));
frame.getContentPane().add(emptyLabel, BorderLayout.CENTER);
frame.setLocation((int)dimension.getWidth()/4, (int)dimension.getHeight()/4);
</code></pre>

The JLabel sets the screen-size. It's in FrameDemo.java available on the java tutorials at the Oracle/Sun site. I set it to half the screen size's height/width. Then, I centered it by placing the top left at 1/4 of the screen size's dimension from the left, and 1/4 of the screen size's dimension from the top. You can use a similar concept.

blocks|key|1738668|text|下面是用于在现有窗口的顶部中心显示框架的代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1738669|public+class+SwingContainerDemo+{

private+JFrame+mainFrame;

private+JPanel+controlPanel;

private+JLabel+msglabel;

Frame.setLayout(new+FlowLayout());

++mainFrame.addWindowListener(new+WindowAdapter()+{
+++++public+void+windowClosing(WindowEvent+windowEvent){
++++++++System.exit(0);
+++++}++++++++
++});++++
++//headerLabel+=+new+JLabel("",+JLabel.CENTER);++++++++
+/*+statusLabel+=+new+JLabel("",JLabel.CENTER);++++
++statusLabel.setSize(350,100);
+*/+msglabel+=+new+JLabel("Welcome+to+TutorialsPoint+SWING+Tutorial.",+JLabel.CENTER);

++controlPanel+=+new+JPanel();
++controlPanel.setLayout(new+FlowLayout());

++//mainFrame.add(headerLabel);
++mainFrame.add(controlPanel);
+//+mainFrame.add(statusLabel);

++mainFrame.setUndecorated(true);
++mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
++mainFrame.getRootPane().setWindowDecorationStyle(JRootPane.NONE);
++mainFrame.setVisible(true);++

++centreWindow(mainFrame);|code-block|syntax|javascript|1738670|}|1738671|public+static+void+centreWindow(Window+frame)+{
++++Dimension+dimension+=+Toolkit.getDefaultToolkit().getScreenSize();
++++int+x+=+(int)+((dimension.getWidth()+-+frame.getWidth())+/+2);
++++int+y+=+(int)+((dimension.getHeight()+-+frame.getHeight())+/+2);
++++frame.setLocation(x,+0);
}


public+void+showJFrameDemo(){
+/*+headerLabel.setText("Container+in+action:+JFrame");+++*/
++final+JFrame+frame+=+new+JFrame();
++frame.setSize(300,+300);
++frame.setLayout(new+FlowLayout());+++++++
++frame.add(msglabel);

++frame.addWindowListener(new+WindowAdapter()+{
+++++public+void+windowClosing(WindowEvent+windowEvent){
++++++++frame.dispose();
+++++}++++++++
++});++++



++JButton+okButton+=+new+JButton("Capture");
++okButton.addActionListener(new+ActionListener()+{
+++++public+void+actionPerformed(ActionEvent+e)+{
++//++++++statusLabel.setText("A+Frame+shown+to+the+user.");
++++++//++frame.setVisible(true);
++++++++mainFrame.setState(Frame.ICONIFIED);
++++++++Robot+robot+=+null;
++++++++try+{
++++++++++++robot+=+new+Robot();
++++++++}+catch+(AWTException+e1)+{
++++++++++++//+TODO+Auto-generated+catch+block
++++++++++++e1.printStackTrace();
++++++++}
++++++++final+Dimension+screenSize+=+Toolkit.getDefaultToolkit().
++++++++++++++++getScreenSize();
++++++++final+BufferedImage+screen+=+robot.createScreenCapture(
++++++++++++++++new+Rectangle(screenSize));

++++++++SwingUtilities.invokeLater(new+Runnable()+{
++++++++++++public+void+run()+{
++++++++++++++++new+ScreenCaptureRectangle(screen);
++++++++++++}
++++++++});
++++++++mainFrame.setState(Frame.NORMAL);
+++++}
++});
++controlPanel.add(okButton);
++mainFrame.setVisible(true);++|1738672|}公共静态空main(String[]+args)引发异常{|1738673|new+SwingContainerDemo().showJFrameDemo();|1738674|1738675|以下是上述代码片段的输出：|1738676|📷|atomic|offset|length|1738677|​|1738678|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/48fa14bce4b9e4fa8fd86684a605f92f.png|imageAlt^0|0|0|0|0|0|0|0|0|0|1|0|0|0^^$0|@$1|2|3|4|5|6|7|17|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|18|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|19|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|1A|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|1B|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|1C|8|@]|9|@]|A|$E|F]]|$1|O|3|H|5|6|7|1D|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|1E|8|@]|9|@]|A|$]]|$1|R|3|S|5|T|7|1F|8|@]|9|@$U|1G|V|1H|1|1I]]|A|$]]|$1|W|3|X|5|6|7|1J|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15|16|-4]]]]

below is code for displaying a frame at top-centre of existing window.

<pre><code>public class SwingContainerDemo {

private JFrame mainFrame;

private JPanel controlPanel;

private JLabel msglabel;

Frame.setLayout(new FlowLayout());

 mainFrame.addWindowListener(new WindowAdapter() {
 public void windowClosing(WindowEvent windowEvent){
 System.exit(0);
 } 
 }); 
 //headerLabel = new JLabel("", JLabel.CENTER); 
 /* statusLabel = new JLabel("",JLabel.CENTER); 
 statusLabel.setSize(350,100);
 */ msglabel = new JLabel("Welcome to TutorialsPoint SWING Tutorial.", JLabel.CENTER);

 controlPanel = new JPanel();
 controlPanel.setLayout(new FlowLayout());

 //mainFrame.add(headerLabel);
 mainFrame.add(controlPanel);
 // mainFrame.add(statusLabel);

 mainFrame.setUndecorated(true);
 mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 mainFrame.getRootPane().setWindowDecorationStyle(JRootPane.NONE);
 mainFrame.setVisible(true); 

 centreWindow(mainFrame);
</code></pre>

}

<pre><code>public static void centreWindow(Window frame) {
 Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
 int x = (int) ((dimension.getWidth() - frame.getWidth()) / 2);
 int y = (int) ((dimension.getHeight() - frame.getHeight()) / 2);
 frame.setLocation(x, 0);
}


public void showJFrameDemo(){
 /* headerLabel.setText("Container in action: JFrame"); */
 final JFrame frame = new JFrame();
 frame.setSize(300, 300);
 frame.setLayout(new FlowLayout()); 
 frame.add(msglabel);

 frame.addWindowListener(new WindowAdapter() {
 public void windowClosing(WindowEvent windowEvent){
 frame.dispose();
 } 
 }); 



 JButton okButton = new JButton("Capture");
 okButton.addActionListener(new ActionListener() {
 public void actionPerformed(ActionEvent e) {
 // statusLabel.setText("A Frame shown to the user.");
 // frame.setVisible(true);
 mainFrame.setState(Frame.ICONIFIED);
 Robot robot = null;
 try {
 robot = new Robot();
 } catch (AWTException e1) {
 // TODO Auto-generated catch block
 e1.printStackTrace();
 }
 final Dimension screenSize = Toolkit.getDefaultToolkit().
 getScreenSize();
 final BufferedImage screen = robot.createScreenCapture(
 new Rectangle(screenSize));

 SwingUtilities.invokeLater(new Runnable() {
 public void run() {
 new ScreenCaptureRectangle(screen);
 }
 });
 mainFrame.setState(Frame.NORMAL);
 }
 });
 controlPanel.add(okButton);
 mainFrame.setVisible(true); 
</code></pre>

}
 public static void main(String[] args) throws Exception {

<pre><code>new SwingContainerDemo().showJFrameDemo();
</code></pre>

}

Below is the ouput of above code-snippet:<a href="https://i.stack.imgur.com/BvcfS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BvcfS.png" alt="enter image description here"></a>

blocks|key|1738710|text|示例:在myWindow()内的第3行是将窗口设置在屏幕中央所需的代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1738711|JFrame+window;

public+myWindow()+{

++++window+=+new+JFrame();
++++window.setSize(1200,800);
++++window.setLocationRelativeTo(null);+//+this+line+set+the+window+in+the+center+of+thr+screen
++++window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
++++window.getContentPane().setBackground(Color.BLACK);
++++window.setLayout(null);+//+disable+the+default+layout+to+use+custom+one.
++++window.setVisible(true);+//+to+show+the+window+on+the+screen.
}|code-block|syntax|javascript|1738712|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Example: Inside myWindow() on line 3 is the code you need to set the window in the center of the screen. 

<pre><code>JFrame window;

public myWindow() {

 window = new JFrame();
 window.setSize(1200,800);
 window.setLocationRelativeTo(null); // this line set the window in the center of thr screen
 window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 window.getContentPane().setBackground(Color.BLACK);
 window.setLayout(null); // disable the default layout to use custom one.
 window.setVisible(true); // to show the window on the screen.
}
</code></pre>

blocks|key|1523488|text|下面的代码将Window置于当前监视器的中心(即鼠标指针所在的位置)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1523489|public+static+final+void+centerWindow(final+Window+window)+{
++++GraphicsDevice+screen+=+MouseInfo.getPointerInfo().getDevice();
++++Rectangle+r+=+screen.getDefaultConfiguration().getBounds();
++++int+x+=+(r.width+-+window.getWidth())+/+2+%2B+r.x;
++++int+y+=+(r.height+-+window.getHeight())+/+2+%2B+r.y;
++++window.setLocation(x,+y);
}|code-block|syntax|javascript|1523490|entityMap^0|6|6|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

The following code center the <code>Window</code> in the center of the current monitor (ie where the mouse pointer is located).

<pre><code>public static final void centerWindow(final Window window) {
 GraphicsDevice screen = MouseInfo.getPointerInfo().getDevice();
 Rectangle r = screen.getDefaultConfiguration().getBounds();
 int x = (r.width - window.getWidth()) / 2 + r.x;
 int y = (r.height - window.getHeight()) / 2 + r.y;
 window.setLocation(x, y);
}
</code></pre>

blocks|key|1738596|text|你也可以试试这个。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1738597|Frame+frame+=+new+Frame("Centered+Frame");
Dimension+dimemsion+=+Toolkit.getDefaultToolkit().getScreenSize();
frame.setLocation(dimemsion.width/2-frame.getSize().width/2,+dimemsion.height/2-frame.getSize().height/2);|code-block|syntax|javascript|1738598|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You could try this also.

<pre class="lang-java prettyprint-override"><code>Frame frame = new Frame("Centered Frame");
Dimension dimemsion = Toolkit.getDefaultToolkit().getScreenSize();
frame.setLocation(dimemsion.width/2-frame.getSize().width/2, dimemsion.height/2-frame.getSize().height/2);
</code></pre>

blocks|key|1523365|text|实际上frame.getHeight()和getwidth()都不返回值，直接用System.out.println(frame.getHeight());检查一下，把宽度和高度的值放在中间就行了。例如:如下所示|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1523366|Dimension+dimension+=+Toolkit.getDefaultToolkit().getScreenSize();++++++
int+x=(int)((dimension.getWidth()+-+450)/2);
int+y=(int)((dimension.getHeight()+-+450)/2);
jf.setLocation(x,+y);++|code-block|syntax|javascript|1523367|这两个450都是我的帧宽度和高度|1523368|entityMap^0|8|C|L|A|14|12|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

Actually frame<code>.getHeight()</code> and <code>getwidth()</code> doesnt return values , check it by <code>System.out.println(frame.getHeight());</code> directly put the values for width and height ,then it will work fine in center. eg: as below

<pre><code>Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize(); 
int x=(int)((dimension.getWidth() - 450)/2);
int y=(int)((dimension.getHeight() - 450)/2);
jf.setLocation(x, y); 
</code></pre>

both 450 is my frame width n height

blocks|key|1523457|text|public+class+SwingExample+implements+Runnable+{

++++@Override
++++public+void+run()+{
++++++++//+Create+the+window
++++++++final+JFrame+f+=+new+JFrame("Hello,+World!");
++++++++SwingExample.centerWindow(f);
++++++++f.setPreferredSize(new+Dimension(500,+250));
++++++++f.setMaximumSize(new+Dimension(10000,+200));
++++++++f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
++++}

++++public+static+void+centerWindow(JFrame+frame)+{
++++++++Insets+insets+=+frame.getInsets();
++++++++frame.setSize(new+Dimension(insets.left+%2B+insets.right+%2B+500,+insets.top+%2B+insets.bottom+%2B+250));
++++++++frame.setVisible(true);
++++++++frame.setResizable(false);

++++++++Dimension+dimension+=+Toolkit.getDefaultToolkit().getScreenSize();
++++++++int+x+=+(int)+((dimension.getWidth()+-+frame.getWidth())+/+2);
++++++++int+y+=+(int)+((dimension.getHeight()+-+frame.getHeight())+/+2);
++++++++frame.setLocation(x,+y);
++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1523458|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre class="lang-java prettyprint-override"><code>public class SwingExample implements Runnable {

 @Override
 public void run() {
 // Create the window
 final JFrame f = new JFrame("Hello, World!");
 SwingExample.centerWindow(f);
 f.setPreferredSize(new Dimension(500, 250));
 f.setMaximumSize(new Dimension(10000, 200));
 f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 }

 public static void centerWindow(JFrame frame) {
 Insets insets = frame.getInsets();
 frame.setSize(new Dimension(insets.left + insets.right + 500, insets.top + insets.bottom + 250));
 frame.setVisible(true);
 frame.setResizable(false);

 Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
 int x = (int) ((dimension.getWidth() - frame.getWidth()) / 2);
 int y = (int) ((dimension.getHeight() - frame.getHeight()) / 2);
 frame.setLocation(x, y);
 }
}
</code></pre>

What's the easiest way to centre a <code>java.awt.Window</code>, such as a <code>JFrame</code> or a <code>JDialog</code>?

问如何在Java中居中显示窗口？
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回答 13

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问如何在Java中居中显示窗口？EN

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问如何在Java中居中显示窗口？
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