[转载]布局管理器GridBagLayout的使用

[J] 布局管理器 GridBagLayout 的使用

Java布局管理器有FlowLayout, BorderLayout, GridLayout, CardLayout, GridBagLayout等，相比较而言，GridBagLayout的使用方式要复杂一些。但它的表现力也最丰富。之前我对GridBagLayout的使用也是一知半解，具体的用法不是十分的明了。这两天认真的看了这一块，就写了下来。 使用 GridBagLayout的主要工作就是设置组件的约束，通过GridBagConstraints的实例设置。 GridBagConstraints 主要有11个参数：gridx, gridy, gridwidth ,gridheight ,anchor ,fill ,weightx ,weighty ,insets ,ipadx ,ipady； 每个参数的意义可以参考java api上的说明。本文的最后附有anchor属性和fill属性的示例。实际使用中根据自己的需要设置特定的属性。 在Java api中给出了一个GridBagLayout的例子和实现，下面的是自己的实现方式。 [CODE] import java.awt.*; import java.awt.event.*; import java.applet.*; public class GridBagLayoutDemo extends Applet { GridBagLayout gbaglayout; GridBagConstraints constraints; public void init() {    gbaglayout = new GridBagLayout();      constraints = new GridBagConstraints();    setLayout(gbaglayout);       //Button 1    Button btn1 = new Button("Button01");    constraints.gridx = 0;    constraints.gridy = 0;    constraints.gridwidth = 1;    constraints.gridheight = 1;    constraints.anchor = GridBagConstraints.CENTER;    constraints.fill = GridBagConstraints.NONE;    constraints.weightx = 0.0;    constraints.weighty = 0.0;    constraints.insets = new Insets(0, 0, 0, 0);    constraints.ipadx = 0;    constraints.ipady = 0;    makeButton(gbaglayout, constraints, btn1);       //Button 2    Button btn2 = new Button("Button02");    constraints.gridx = 1;      makeButton(gbaglayout, constraints, btn2);       //Button 3    Button btn3 = new Button("Button03");    constraints.gridx = 2;      makeButton(gbaglayout, constraints, btn3);       //Button 4    Button btn4 = new Button("Button04");    constraints.gridx = 3;      makeButton(gbaglayout, constraints, btn4);    //Button 5    Button btn5 = new Button("Button05");    constraints.gridx = 0;    constraints.gridy = 1;    constraints.gridwidth = 4;    makeButton(gbaglayout, constraints, btn5);       //Button 6    Button btn6 = new Button("Button06");    constraints.gridx = 0;    constraints.gridy = 2;    constraints.gridwidth = 3;    makeButton(gbaglayout, constraints, btn6);       //Button 7    Button btn7 = new Button("Button07");    constraints.gridx = 3;    constraints.gridy = 2;    constraints.gridwidth = 1;    makeButton(gbaglayout, constraints, btn7);       //Button 8    Button btn8 = new Button("Button08");    constraints.gridx = 0;    constraints.gridy = 3;    constraints.gridwidth = 1;    constraints.gridheight = 2;      makeButton(gbaglayout, constraints, btn8);       //Button 9    Button btn9 = new Button("Button09");    constraints.gridx = 1;    constraints.gridy = 3;    constraints.gridwidth = 3;    constraints.gridheight = 1;      makeButton(gbaglayout, constraints, btn9);       //Button 10    Button btn10 = new Button("Button10");    constraints.gridx = 1;    constraints.gridy = 4;    constraints.gridwidth = 3;    constraints.gridheight = 1;      makeButton(gbaglayout, constraints, btn10); } private void makeButton(GridBagLayout gbaglayout, GridBagConstraints constraints, Component component) {    gbaglayout.setConstraints(component, constraints);    add(component); } public static void main(String[] args) {    Frame frame = new Frame("GridBagLayoutDemo");    frame.addWindowListener(new WindowAdapter() {     public void windowClosing(WindowEvent e) {      System.exit(0);     }    });       GridBagLayoutDemo demo = new GridBagLayoutDemo();    demo.init();       frame.add(BorderLayout.CENTER, demo);    frame.setSize(270, 150);    //frame.setSize(361, 254);    frame.setVisible(true);   } } [CODE] 显示窗口可以如图所示划分为 5 行和 4 列，每个按钮所在的单元可以很容易的确定，所以 gridx 和 gridy 的值都很容易确定，组件放置在的位置也就确定了。 然而，组件都有一个默认的大小，它和它所在的单元格大小一般情况下都是不同的，并且如果窗口发生变化时，组件做出什么样的改变就要用到fill ,weightx 和 weighty了。 结合具体的例子来看： 设置 Button 1 //Button 1 Button btn1 = new Button("Button01"); //所在单元格为(0, 0) constraints.gridx = 0; constraints.gridy = 0; //占用一个长度长和一个长度宽 constraints.gridwidth = 1; constraints.gridheight = 1; //这里使用默认的 anchor constraints.anchor = GridBagConstraints.CENTER; //设置NONE填充 constraints.fill = GridBagConstraints.NONE; //设置填充权重 constraints.weightx = 0.0; constraints.weighty = 0.0; //Insets, ipadx, ipady使用默认值 constraints.insets = new Insets(0, 0, 0, 0); constraints.ipadx = 0; constraints.ipady = 0; //添加 Button01 按钮 makeButton(gbaglayout, constraints, btn1);   设置 Button02, Button03, Button04   //Button 2 Button btn2 = new Button("Button02"); constraints.gridx = 1;   makeButton(gbaglayout, constraints, btn2); //Button 3 Button btn3 = new Button("Button03"); constraints.gridx = 2;   makeButton(gbaglayout, constraints, btn3); //Button 4 Button btn4 = new Button("Button04"); constraints.gridx = 3;   makeButton(gbaglayout, constraints, btn4); Button02, Button03, Button04和Button01的区别是，只需要设置他们的gridx值;其他的不变。   设置 Button05 //Button 5 Button btn5 = new Button("Button05"); //所在单元格为(0, 1) constraints.gridx = 0; constraints.gridy = 1; //占用了所有的4个单元格宽度 ，一个单元格高，省略没写 constraints.gridwidth = 4; makeButton(gbaglayout, constraints, btn5);   设置 Button06 //Button 6 Button btn6 = new Button("Button06"); //所在单元格为(0, 2) constraints.gridx = 0; constraints.gridy = 2; //占用了所有的3个单元格宽度 ，一个单元格高，省略没写 constraints.gridwidth = 3; makeButton(gbaglayout, constraints, btn6);   设置 Button07 //Button 7 Button btn7 = new Button("Button07"); //所在单元格为(3, 2) constraints.gridx = 3; constraints.gridy = 2; //占用了所有的1个单元格宽度 ，一个单元格高，省略没写 constraints.gridwidth = 1; makeButton(gbaglayout, constraints, btn7);   设置 Button08 //Button 8 Button btn8 = new Button("Button08"); //所在单元格为(0, 3) constraints.gridx = 0; constraints.gridy = 3; //占用了所有的1个单元格宽度 ，2个单元格高 constraints.gridwidth = 1; constraints.gridheight = 2;    makeButton(gbaglayout, constraints, btn8);   设置 Button09 //Button 9 Button btn9 = new Button("Button09"); //所在单元格为(1, 3) constraints.gridx = 1; constraints.gridy = 3; //占用了所有的3个单元格宽度 ，1个单元格高 constraints.gridwidth = 3; constraints.gridheight = 1;    makeButton(gbaglayout, constraints, btn9);   设置 Button10 //Button 10 Button btn10 = new Button("Button10"); //所在单元格为(1, 4) constraints.gridx = 1; constraints.gridy = 4; //占用了所有的3个单元格宽度 ，1个单元格高，由于和Button09一样，也可以不写 constraints.gridwidth = 3; constraints.gridheight = 1;    makeButton(gbaglayout, constraints, btn10); 设置好10个按钮之后，看看结果如何： 和目标差别还很大,但它确实是按照期望的方式，在特定的单元格内显示了。 为什么有差别呢？原因是单元格比按钮默认的大小要大，没有设置fill方式。 由于需要Button01, Button02, Button03 和 Button04的长度充满单元格，可修改 fill 属性为：constraints.fill = GridBagConstraints.HORIZONTAL; 同时改变constraints.weightx = 1.0;使得窗口变化时按钮能随之伸长(如果不改变weightx值，改变窗口大小时，看看会有什么效果)。 显示结果： 可以看到 Button08有问题，更改相应部分： //Button 8 Button btn8 = new Button("Button08"); constraints.gridx = 0; constraints.gridy = 3; constraints.gridwidth = 1; constraints.gridheight = 2; //设置Button08的 fill 为 BOTH constraints.fill = GridBagConstraints.BOTH;   constraints.weightx = 1.0; constraints.weighty = 1.0; makeButton(gbaglayout, constraints, btn8); //Button09 Button btn9 = new Button("Button09"); constraints.gridx = 1; constraints.gridy = 3; constraints.gridwidth = 3; constraints.gridheight = 1; //不需要垂直变化 constraints.fill = GridBagConstraints.HORIZONTAL; constraints.weightx = 1.0; constraints.weighty = 0.0; makeButton(gbaglayout, constraints, btn9); //Button 10 Button btn10 = new Button("Button10"); constraints.gridx = 1; constraints.gridy = 4; constraints.gridwidth = 3; constraints.gridheight = 1;   //需要垂直变化 constraints.fill = GridBagConstraints.BOTH; constraints.weightx = 1.0; constraints.weighty = 1.0; makeButton(gbaglayout, constraints, btn10); 好了，所有的属性设置好了。     完整代码： [CODE] import java.awt.*; import java.awt.event.*; import java.applet.*; public class GridBagLayoutDemo extends Applet { GridBagLayout gbaglayout; GridBagConstraints constraints; public void init() {    gbaglayout = new GridBagLayout();      constraints = new GridBagConstraints();    setLayout(gbaglayout);       //Button 1    Button btn1 = new Button("Button01");    constraints.gridx = 0;    constraints.gridy = 0;    constraints.gridwidth = 1;    constraints.gridheight = 1;    constraints.anchor = GridBagConstraints.CENTER;      constraints.fill = GridBagConstraints.HORIZONTAL;    constraints.weightx = 1.0;    constraints.weighty = 0.0;    constraints.insets = new Insets(0, 0, 0, 0);    constraints.ipadx = 0;    constraints.ipady = 0;    makeButton(gbaglayout, constraints, btn1);      //Button 2    Button btn2 = new Button("Button02");    constraints.gridx = 1;      makeButton(gbaglayout, constraints, btn2);       //Button 3    Button btn3 = new Button("Button03");    constraints.gridx = 2;      makeButton(gbaglayout, constraints, btn3);       //Button 4    Button btn4 = new Button("Button04");    constraints.gridx = 3;      makeButton(gbaglayout, constraints, btn4);       //Button 5    Button btn5 = new Button("Button05");    constraints.gridx = 0;    constraints.gridy = 1;    constraints.gridwidth = 4;    makeButton(gbaglayout, constraints, btn5);       //Button 6    Button btn6 = new Button("Button06");    constraints.gridx = 0;    constraints.gridy = 2;    constraints.gridwidth = 3;    makeButton(gbaglayout, constraints, btn6);       //Button 7    Button btn7 = new Button("Button07");    constraints.gridx = 3;    constraints.gridy = 2;    constraints.gridwidth = 1;    makeButton(gbaglayout, constraints, btn7);       //Button 8    Button btn8 = new Button("Button08");    constraints.gridx = 0;    constraints.gridy = 3;    constraints.gridwidth = 1;    constraints.gridheight = 2;    constraints.fill = GridBagConstraints.BOTH;    constraints.weightx = 1.0;    constraints.weighty = 1.0;        makeButton(gbaglayout, constraints, btn8);    //Button 9    Button btn9 = new Button("Button09");    constraints.gridx = 1;    constraints.gridy = 3;    constraints.gridwidth = 3;    constraints.gridheight = 1;      constraints.fill = GridBagConstraints.HORIZONTAL;    constraints.weightx = 1.0;    constraints.weighty = 0.0;    makeButton(gbaglayout, constraints, btn9);      //Button 10    Button btn10 = new Button("Button10");    constraints.gridx = 1;    constraints.gridy = 4;    constraints.gridwidth = 3;    constraints.gridheight = 1;      constraints.fill = GridBagConstraints.BOTH;    constraints.weightx = 1.0;    constraints.weighty = 1.0;    makeButton(gbaglayout, constraints, btn10); } private void makeButton(GridBagLayout gbaglayout, GridBagConstraints constraints, Component component) {    gbaglayout.setConstraints(component, constraints);    add(component); } public static void main(String[] args) {    Frame frame = new Frame("GridBagLayoutDemo");    frame.addWindowListener(new WindowAdapter() {     public void windowClosing(WindowEvent e) {      System.exit(0);     }    });       GridBagLayoutDemo demo = new GridBagLayoutDemo();    demo.init();       frame.add(BorderLayout.CENTER, demo);    frame.setSize(270, 150);    //frame.setSize(361, 254);    frame.setVisible(true);   } } [CODE] 以下是 fill 和 anchor 的示例： fill的4种方式：   anchor的9种方式：