GridBagLayout

GridBagLayout:网格袋布局管理器，它不要求组件的大小相同便可以将组件垂直、水平或沿它们的基线对齐。每个GridBagLayout对象维持一个动态的矩形单元格(动态计算出单元格的大小)，每个组件占用一个或多个单元格，该单元格被称为显示区域。每个组件显示区域按从左到右、从上到下依次排列。

GridBagConstraints：封装了若干对组件的约束属性，每个由GridBagLayout管理的组件都关联一个该约束实例，以指定组件所在显示区域的具体放置位置，以及组件在其显示区域中的对齐方式。给组件添加约束：GridBagLayout.setConstraints(Component comp, GridBagConstraints c)。

GridBagConstraints属性：

1. gridx,gridy 组件显示区域 开始显示的位置（单元格坐标），容器左上角第一个单元格位置为 (0, 0)，默认值为RELATIVE，表示放置在 “上一个组件”（所在行列最后添加的一个组件）的 “后面”。
2. gridwidth,gridheight 组件显示区域 水平/竖直方向 所占单元格的个数，默认值为 1，如要占多行/列，需整体结果有足够的行/列。有如下两个常量特殊值可选:
   REMAINDER: 占完所在行/列余下所有单元格（该值可实现 换行 作用）；
   RELATIVE: 占到所在行/列余下的倒数第二个单元格（使用该值，所在行/列的最后一个单元格需要“合理”安排组件，并手动换行）。设置该值不能导致 “前面” 或 “后面” 单元格有留空白，否则可能无效。
3. weightx,weighty 如何分布额外空间(单元格区域外，容器边缘内的间隔)，当制定行/列中的其中任意一个组件的权重大于0，则该行/列将(和其他行/列按权重比例)分配额外的水平/竖直空间。当权重为0时，则整个单元格区域居中于容器中心。
4. fill 当显示区域大小大于组件所需要的大小时，组件在其显示区域内的填充方式。可能的值如下：NONE：不调整组件大小；HORIZONTAL：加宽组件，使它在水平方向上填满其显示区域，但是不改变高度；VERTICAL：加高组件，使它在垂直方向上填满其显示区域，但是不改变宽度；BOTH:使组件完全填满其显示区域。
5. anchor
6. ipadx,ipady 组件的内部填充(可看做组件的内边距)，即对组件最大大小的添加量。
7. insets 组件的外部填充(可看做是组件的外边距，也可以看做是显示区域的内边距)。

预期界面：

　　

实现代码：

private JPanel panelResult;
    private JPanel panelM;
    private JPanel panelParam;

    private JTextField textFieldResult;

    private JButton buttonMC;
    private JButton buttonMR;
    private JButton buttonMPlus;
    private JButton buttonMDec;
    private JButton buttonMs;
    private JButton buttonM;
    private JButton buttonCE;
    private JButton buttonC;
    private JButton buttonClear;
    private JButton buttonDIV;
    private JButton button7;
    private JButton button8;
    private JButton button9;
    private JButton buttonMUL;
    private JButton button4;
    private JButton button5;
    private JButton button6;
    private JButton buttonDec;
    private JButton button1;
    private JButton button2;
    private JButton button3;
    private JButton buttonAdd;
    private JButton buttonMinus;
    private JButton button0;
    private JButton buttonPoint;
    private JButton buttonEqual;

private void initCompents() {
        this.textFieldResult = new JTextField();
        this.textFieldResult.setBackground(Color.GRAY);
        this.textFieldResult.setForeground(Color.white);
        this.textFieldResult.setFont(new Font(Font.SERIF, Font.BOLD, 32));
        this.textFieldResult.setHorizontalAlignment(SwingConstants.RIGHT);
        this.textFieldResult.setEnabled(false);
        this.textFieldResult.setText("0");

        this.buttonMC = new JButton("MC");
        this.buttonMR = new JButton("MR");
        this.buttonMPlus = new JButton("M+");
        this.buttonMDec = new JButton("M-");
        this.buttonMs = new JButton("MS");
        this.buttonM = new JButton("M`");

        this.buttonCE = new JButton("CE");
        this.buttonC = new JButton("C");
        this.buttonClear = new JButton("Clear");
        this.buttonDIV = new JButton("/");
        this.button7 = new JButton("7");
        this.button8 = new JButton("8");
        this.button9 = new JButton("9");
        this.buttonMUL = new JButton("*");
        this.button4 = new JButton("4");
        this.button5 = new JButton("5");
        this.button6 = new JButton("6");
        this.buttonDec = new JButton("-");
        this.button1 = new JButton("1");
        this.button2 = new JButton("2");
        this.button3 = new JButton("3");
        this.buttonMinus = new JButton("+_");
        this.button0 = new JButton("0");
        this.buttonPoint = new JButton(".");
        this.buttonEqual = new JButton("=");
        this.buttonAdd = new JButton("+");

        this.panelM = new JPanel();
        this.panelParam = new JPanel();
        this.panelResult = new JPanel();

    }

    private void initLayout() {
        this.setSize(420, 500);
        this.setLocationRelativeTo(null);
        this.getContentPane().setLayout(new GridBagLayout());
        this.setTitle("计算器");

        this.getContentPane().add(panelResult, new GridBagConstraintsHelper(0, 0, 1, 1).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.getContentPane().add(panelM, new GridBagConstraintsHelper(0, 1, 1, 1).setWeight(1, 0).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.getContentPane().add(panelParam, new GridBagConstraintsHelper(0, 3, 1, 1).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));

        this.panelResult.setLayout(new GridBagLayout());
        this.panelResult.add(this.textFieldResult, new GridBagConstraintsHelper(0, 0, 1, 1).setInsets(5, 1, 0, 1).setIpad(0, 30).setWeight(1, 1).setAnchor(GridBagConstraints.CENTER).setFill(GridBagConstraints.BOTH));

        this.panelM.setLayout(new GridBagLayout());
        this.panelM.add(this.buttonMC, new GridBagConstraintsHelper(0, 0, 1, 1).setInsets(1).setWeight(1, 1).setAnchor(GridBagConstraints.CENTER).setFill(GridBagConstraints.BOTH));
        this.panelM.add(this.buttonMR, new GridBagConstraintsHelper(1, 0, 1, 1).setInsets(1).setWeight(1, 1).setAnchor(GridBagConstraints.CENTER).setFill(GridBagConstraints.BOTH));
        this.panelM.add(this.buttonMPlus, new GridBagConstraintsHelper(2, 0, 1, 1).setInsets(1).setWeight(1, 1).setAnchor(GridBagConstraints.CENTER).setFill(GridBagConstraints.BOTH));
        this.panelM.add(this.buttonMDec, new GridBagConstraintsHelper(3, 0, 1, 1).setInsets(1).setWeight(1, 1).setAnchor(GridBagConstraints.CENTER).setFill(GridBagConstraints.BOTH));
        this.panelM.add(this.buttonMs, new GridBagConstraintsHelper(4, 0, 1, 1).setInsets(1).setWeight(1, 1).setAnchor(GridBagConstraints.CENTER).setFill(GridBagConstraints.BOTH));
        this.panelM.add(this.buttonM, new GridBagConstraintsHelper(5, 0, 1, 1).setInsets(1).setWeight(1, 1).setAnchor(GridBagConstraints.CENTER).setFill(GridBagConstraints.BOTH));

        this.panelParam.setLayout(new GridBagLayout());
        this.panelParam.add(this.buttonCE, new GridBagConstraintsHelper(0, 0, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.buttonC, new GridBagConstraintsHelper(1, 0, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.buttonClear, new GridBagConstraintsHelper(2, 0, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.buttonDIV, new GridBagConstraintsHelper(3, 0, 1, 1).setInsets(1).setIpad(5, 20).setWeight(2, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.button7, new GridBagConstraintsHelper(0, 1, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.button8, new GridBagConstraintsHelper(1, 1, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.button9, new GridBagConstraintsHelper(2, 1, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.buttonMUL, new GridBagConstraintsHelper(3, 1, 1, 1).setInsets(1).setIpad(5, 20).setWeight(2, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.button4, new GridBagConstraintsHelper(0, 2, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.button5, new GridBagConstraintsHelper(1, 2, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.button6, new GridBagConstraintsHelper(2, 2, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.buttonDec, new GridBagConstraintsHelper(3, 2, 1, 1).setInsets(1).setIpad(5, 20).setWeight(2, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.button1, new GridBagConstraintsHelper(0, 3, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.button2, new GridBagConstraintsHelper(1, 3, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.button3, new GridBagConstraintsHelper(2, 3, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.buttonAdd, new GridBagConstraintsHelper(3, 3, 1, 1).setInsets(1).setIpad(5, 20).setWeight(2, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.buttonMinus, new GridBagConstraintsHelper(0, 4, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.button0, new GridBagConstraintsHelper(1, 4, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.buttonPoint, new GridBagConstraintsHelper(2, 4, 1, 1).setInsets(1).setIpad(5, 20).setWeight(1, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));
        this.panelParam.add(this.buttonEqual, new GridBagConstraintsHelper(3, 4, 1, 1).setInsets(1).setIpad(5, 20).setWeight(2, 1).setAnchor(GridBagConstraints.WEST).setFill(GridBagConstraints.BOTH));

    }