以下代码有什么问题?为什么矩形不显示
public class SynapsePermanencesViewer {
public JPanel createContentPane(Region region) {
JPanel synapseLayer = new JPanel();
synapseLayer.setLayout(null);
Column[][] columns = region.getColumns();
JPanel redSquare = new JPanel();
Color color = new Color(128, 0, 0);
redSquare.setBackground(color);
int squareLength = 50;
redSquare.setSize(squareLength, squareLength);
// calculate the correct location
redSquare.setLocation(150, 150); // <==== This square isn't displaying WHY???
synapseLayer.setOpaque(true);
return synapseLayer;
}
public SynapsePermanencesViewer(Region region) {
JFrame frame = new JFrame("Synapse Permanences Viewer");
frame.setContentPane(this.createContentPane(region));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
Region parentRegion = new Region("parentRegion", 2, 2, 1, 20, 1);
Region childRegion = new Region("childRegion", 4, 4, 1, 20, 3);
RegionToRegionConnect connectType = new RegionToRegionRectangleConnect();
connectType.connect(childRegion, parentRegion, 0, 0);
SynapsePermanencesViewer object = new SynapsePermanencesViewer(parentRegion);
}
}
答案 0 :(得分:2)
您不会将redSquare添加到synapseLayer。
即使您确实添加了它也不会显示的方块,因为synapseLayer使用的是null布局,因此该面板的大小为(0,0)。因此,当您打包框架时,没有任何东西可以显示。
不要使用空布局!让布局管理器为您确定面板的大小,以便pack()方法正常工作。