我想使用数据库动态创建jcomponents。当我打开任何jframe或jpanel组件,如jlabel,jtextfields,jcombobox等应该通过读取数据库行来创建。 我很困惑如何从数据库值引用,即在字符串中引用jcomponent的对象。 这是我的数据库表
try{
con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db","root","pass");
stat = con.createStatement();
ResultSet rs = stat.executeQuery("select * from design");
while(rs.next()){
jTextField1 = new JTextField();
jTextField1.setSize(rs.getInt("height"),rs.getInt("width"));
jTextField1.setLocation(rs.getInt("x"), rs.getInt("y"));
}
rs.close();
stat.close();
con.close();
}
catch(Exception e){
System.out.println(e);
}
这是演示表。 我知道这不起作用,因为我无法与对象和数据库进行通信。 我想在jframe上打印jcomponents。我会写for循环来多次打印它们。 请帮帮我。
答案 0 :(得分:2)
首先看看@ AndrewThompson的明智建议:
Java GUI可能必须在不同的平台上工作 屏幕分辨率&使用不同的PLAF。因此他们不是 有助于准确放置组件。组织组件 对于健壮的GUI,而是使用布局管理器或其组合 它们,以及布局填充和白色空间的边界。
有一些有用的主题可以理解它的含义:
您非常不鼓励使用setLocation()
,setBounds()
或setSize()
等方法。但是,在应用于允许自定义表单之前,我已经看过这种方法。但是,您可以存储GridBagLayout的约束,而不是特定的(x,y)坐标和固定的(宽度,高度)。我们假设您有一张这样的表:
我首先从一个类开始从数据库中包装数据:
public class Data {
private String componentType, text;
private int column, row, width, height, weightX, weightY;
public Data(String componentType, int column, int row, int width, int height
,int weightX, int weightY, String text) {
this.componentType = componentType;
this.column = column;
this.row = row;
this.width = width;
this.height = height;
this.weightX = weightX;
this.weightY = weightY;
this.text = text;
}
// getters and setters here
}
由于数据库调用是一项耗时的任务,您必须考虑使用SwingWorker在后台线程中执行数据库调用(耗时的任务),并在Event Dispatch Thread中创建/更新GUI。 / p>
说完之后你可能有这样的事情:
public class Demo {
private JPanel content;
private JFrame frame;
private void createAndShowGUI() {
content = new JPanel(new GridBagLayout());
SwingWorker<Void, Data> worker = new SwingWorker<Void, Data>() {
@Override
protected Void doInBackground() {
try{
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db","root","password");
Statement stat = con.createStatement();
ResultSet rs = stat.executeQuery("select * from TableName");
while(rs.next()){
String componentType = rs.getString("component");
int column = rs.getInt("x");
int row = rs.getInt("y");
int width = rs.getInt("width");
int height = rs.getInt("height");
int weightx = rs.getInt("weightx");
int weighty = rs.getInt("weighty");
String text = rs.getString("text");
Data data = new Data(componentType, column, row, width, height
,weightx, weighty, text);
publish(data);
}
rs.close();
stat.close();
con.close();
} catch(Exception e) {
System.out.println(e);
}
return null;
}
@Override
protected void process(List<Data> chunks) {
for(Data data : chunks) {
JComponent component = null;
if(data.getComponentType().equalsIgnoreCase("JTextField")) {
component = new JTextField(data.getText());
}
if(data.getComponentType().equalsIgnoreCase("JComboBox")) {
component = new JComboBox();
}
if(data.getComponentType().equalsIgnoreCase("JLabel")) {
component = new JLabel(data.getText());
}
if(component != null) {
GridBagConstraints constraints = new GridBagConstraints();
constraints.gridx = data.getColumn();
constraints.gridy = data.getRow();
constraints.gridwidth = data.getWidth();
constraints.gridheight = data.getHeight();
constraints.weightx = data.getWeightX();
constraints.weighty = data.getWeightY();
constraints.anchor = GridBagConstraints.WEST;
constraints.fill = GridBagConstraints.BOTH;
constraints.insets = new Insets(8,8,8,8);
content.add(component, constraints);
}
}
}
@Override
protected void done() {
frame = new JFrame("Demo");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(content);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
};
worker.execute();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new Demo().createAndShowGUI();
}
});
}
}
你会看到这样的事情: