SQL Server如何截断(Truncate)和收缩(Shrink)事务日志

 

 

实现步骤：

      1.  主界面

           主要方法：

           继承JFrame类，并获得其内容面板

           getContentPane();

          

           获得内容面板的画布对象：

           Graphic g=dPane.getGrahpics();

 

          调用重绘方法

          repaint();

          自动调用内部类paint()方法。实现重绘。

      

      2.  添加按钮监听器

           继承鼠标监听器和事件监听器。

 

           重写actionPerformed()等方法

         

      3. 自定义保存与打开按钮时响应的方法

         

 

 

 

 

 

主界面：MainFrame类

 

public class MainFrame extends JFrame {
JPanel cPane;
private List<Graph> List = new ArrayList<Graph>();

/**
* 构造方法，初始化界面
*/
public MainFrame() {
//窗体相关属性
super("画板_1.0");
setSize(1000, 700);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLocationRelativeTo(null);

//获得窗体内容面板
cPane = (JPanel) getContentPane();
cPane.setLayout(new BorderLayout());

JPanel mPane = new JPanel();
JPanel bPane = new JPanel();
JPanel dPane = new DrawPanel();

mPane.setBackground(Color.orange);
bPane.setBackground(Color.DARK_GRAY);
dPane.setBackground(Color.WHITE);

cPane.add(BorderLayout.SOUTH, mPane);
cPane.add(BorderLayout.WEST, bPane);
cPane.add(BorderLayout.CENTER, dPane);

// 菜单以及菜单子项
MenuBar bar = new MenuBar();
Menu m_file = new Menu("File");
Menu m_help = new Menu("Help");
MenuItem mi_new = new MenuItem("New");
MenuItem mi_open = new MenuItem("Open");
MenuItem mi_save = new MenuItem("Save");

m_file.add(mi_new);
m_file.add(mi_open);
m_file.add(mi_save);
bar.add(m_file);
bar.add(m_help);
// 添加菜单栏
setMenuBar(bar);

// 添加按钮
JButton btn_line = new JButton("直线");
JButton btn_curve = new JButton("曲线");
JButton btn_rectangle = new JButton("矩形");
JButton btn_oval = new JButton("圆");
JButton btn_color = new JButton("颜色");

bPane.setLayout(new GridLayout(15, 1));
bPane.add(btn_line);
bPane.add(btn_curve);
bPane.add(btn_rectangle);
bPane.add(btn_oval);
bPane.add(btn_color);

JButton btn_save = new JButton("保存");
JButton btn_open = new JButton("打开");
mPane.add(btn_save);
mPane.add(btn_open);

// 设置窗体可见
setVisible(true);

// 取的画布[
Graphics g = dPane.getGraphics();

// 创建按钮监听对象，并传入画板以及当前窗体
bl = new ButtonListener(g, dPane, this);

// 为按钮添加动作监听器
btn_line.addActionListener(bl);
btn_curve.addActionListener(bl);
btn_rectangle.addActionListener(bl);
btn_oval.addActionListener(bl);
btn_color.addActionListener(bl);
btn_save.addActionListener(bl);
btn_open.addActionListener(bl);
// 为画板添加鼠标监听器的方法
dPane.addMouseListener(bl);
dPane.addMouseMotionListener(bl);
}

class DrawPanel extends JPanel {
/**
* 重绘方法
*/
public void paint(Graphics g) {
super.paint(g);
if (null != bl) {
System.out.println("====-------------->"
+ bl.getGraphList().size());
// 取出队列中保存信息
for (int i = 0; i < bl.getGraphList().size(); i++) {
Graph graph = bl.getGraphList().get(i);
Color c = graph.getColor();
if (graph.getItem().equals("直线")
|| graph.getItem().equals("曲线")) {
g.setColor(c);
g.drawLine(graph.getX1(), graph.getY1(), graph.getX2(),
graph.getY2());

} else if (graph.getItem().equals("矩形")) {
g.setColor(c);
g.fillRect(graph.getX1(), graph.getY1(), graph.getX2(),
graph.getY2());

} else if (graph.getItem().equals("圆")) {
g.setColor(c);
g.fillOval(graph.getX1(), graph.getY1(), graph.getX2(),
graph.getY2());

}
}
}
}
}

/**
* 主方法
*
* @param args
*/
public static void main(String[] args) {
new MainFrame();
}
//自定义按钮监听器
private ButtonListener bl;
}

 

 

 

按钮监听类：ButtonListener类

public class ButtonListener extends MouseAdapter implements ActionListener {
private Graphics g;
private Color color = Color.black;
private JPanel dPane;
private int x1, y1, x2, y2;
private String item = "直线";
private MainFrame mf;

// 定义计数器变量
private int count = 0;
// 创建Graph类型的存储队列
private List<Graph> list = new ArrayList<Graph>();
// 定义保存的路径
String path = "src\\cn\\cjl\\study0428\\drawer\\save.txt";

// 传入画板以及要重绘的容器
public ButtonListener(Graphics g, JPanel dPane, MainFrame mf) {
this.mf = mf;
this.g = g;
this.dPane = dPane;
}

public void Fresh() {
// 调用MainFram的paint()方法
dPane.repaint();
}

/**
* 按钮监听响应方法
*/
public void actionPerformed(ActionEvent e) {
// 判断所选的按钮是否为颜色
if (e.getActionCommand().equals("颜色")) {
color = javax.swing.JColorChooser.showDialog(null, "颜色选择",
Color.black);
} else {
item = e.getActionCommand();
if (item.equals("保存")) {// 保存到文件
SaveOpen so = new SaveOpen();
try {
so.save(path, list);
} catch (IOException e1) {
e1.printStackTrace();
}
} else if (item.equals("打开")) {// 从文件中读取
System.out.println("====>");
SaveOpen so = new SaveOpen();
try {
list = so.open(path);

} catch (IOException e1) {
}
// 刷新
Fresh();
mf.repaint();
}
}
}

// 鼠标按下
public void mousePressed(MouseEvent e) {
// 判断为第一次点击，记录坐标
if (count == 0) {
x1 = e.getX();
y1 = e.getY();
if (!item.equals("曲线")) {
count++;
}
}
// 计数器的值为1，则绘制下列图形
else if (count == 1) {
// 记录第二次点击的坐标值
x2 = e.getX();
y2 = e.getY();
g.setColor(color);
if (item.equals("矩形")) {
g.fillRect(x1, y1, x2, y2);
addGraphList(color, item, x1, y1, x2, y2);
} else if (item.equals("直线")) {
g.drawLine(x1, y1, x2, y2);
addGraphList(color, item, x1, y1, x2, y2);
} else if (item.equals("圆")) {
g.fillOval(x1, y1, x2, y2);
addGraphList(color, item, x1, y1, x2, y2);
}
count--;

}

}

// 鼠标拖动，绘制曲线
public void mouseDragged(MouseEvent e) {
if (item.equals("曲线")) {
x2 = e.getX();
y2 = e.getY();
g.setColor(color);
g.drawLine(x1, y1, x2, y2);
addGraphList(color, item, x1, y1, x2, y2);
// 将最后一个点作为起始坐标
x1 = x2;
y1 = y2;
}
}

/**
* 将图形数据添加到队列中
*/
public void addGraphList(Color color, String item, int x1, int y1, int x2,
int y2) {
Graph graph = new Graph(color, item, x1, y1, x2, y2);
// 添加到队列中
list.add(graph);
}

/**
* 返回队列的方法
*/
public List<Graph> getGraphList() {
return list;
}

}

 

  

封装图像数据类：Graph类

public class Graph {
private int x1,y1,x2,y2;
private Color color;
private String item;
public Graph(Color color,String item,int x1,int y1,int x2,int y2){
this.color=color;
this.item=item;
this.x1=x1;
this.y1=y1;
this.x2=x2;
this.y2=y2;
}
public int getX1() {
return x1;
}
public void setX1(int x1) {
this.x1 = x1;
}
public int getY1() {
return y1;
}
public void setY1(int y1) {
this.y1 = y1;
}
public int getX2() {
return x2;
}
public void setX2(int x2) {
this.x2 = x2;
}
public int getY2() {
return y2;
}
public void setY2(int y2) {
this.y2 = y2;
}
public Color getColor() {
return color;
}
public void setColor(Color color) {
this.color = color;
}
public String getItem() {
return item;
}
public void setItem(String item) {
this.item = item;
}

}

    

 

保存与打开按钮响应方法：SaveOpen类

    

    

public class SaveOpen {
/**
* 保存到文件
* @throws IOException
*/
public void save(String path,List<Graph> list) throws IOException{
//输出流
FileOutputStream fos=new FileOutputStream(path);
//将文件输出流包装成可写基本类型的流
DataOutputStream dos=new DataOutputStream(fos);
System.out.println("--------------------->"+list.size());
dos.writeInt(list.size());
for(int i=0;i<list.size();i++){
Graph graph=list.get(i);
//获取选择图像
String item=graph.getItem();
//定义一个图形变量
int type=0;
//得到坐标值
int x1=graph.getX1();
int y1=graph.getY1();
int x2=graph.getX2();
int y2=graph.getY2();

//判断为圆
if(item.equals("圆")){
type=2;
}

//判断为矩形
else if(item.equals("矩形")){
type=1;
}
//判断为曲线或者直线
else{
type=0;
}
dos.writeInt(type);
dos.writeInt(x1);
dos.writeInt(y1);
dos.writeInt(x2);
dos.writeInt(y2);

//写入颜色
int rgb=graph.getColor().getRGB();
dos.writeInt(rgb);
}
dos.flush();
fos.close();

}

/**
* 读取文件
* @throws IOException
*/
public List<Graph> open(String path) throws IOException{
List<Graph> list=new ArrayList<Graph>();

//输入流
InputStream fis=new FileInputStream(path);
DataInputStream dis=new DataInputStream(fis);

//长度
int len=dis.readInt();
System.out.println("===>"+len);
//循环输出
for(int i=0;i<len;i++){
int type=dis.readInt();
int x1=dis.readInt();
int y1=dis.readInt();
int x2=dis.readInt();
int y2=dis.readInt();

int rgb=dis.readInt();
Color color=new Color(rgb);

if(type==0){
String item="直线";
//实例化Graph对象
Graph graph=new Graph(color,item,x1,y1,x2,y2);
list.add(graph);
}
else if(type==1){
String item="矩形";
//实例化Graph对象
Graph graph=new Graph(color,item,x1,y1,x2,y2);
list.add(graph);
}
else if(type==2){
String item="圆";
//实例化Graph对象
Graph graph=new Graph(color,item,x1,y1,x2,y2);
list.add(graph);
}
}
dis.close();

return list;
}

}