Jpanel inside another Jpanel

问题:

I am facing a problem that i think its pretty easy to solve but i cannot figure it out. So i have a main jpanel and i cannot insert another jpanel2 in a different class to it, the components from jpanel2 dont appear on the 1st one.
Here's the code for the 1st jpanel constructor:

 public PainelPrincipal(Jogo janela) {`  
    super();  
    painel = new JPanel(){  
        protected void paintComponent(java.awt.Graphics g) { 
            super.paintComponents(g); 
            try{  
                g.drawImage(ImageIO.read(PainelPrincipal.class.getResource("Imagens/fundo/Fundo0.jpg")), 0, 0, this);  
            }catch(IOException e){  
                `e.printStackTrace();  
            } 
        };
    };  
    painel.setPreferredSize(new Dimension(1024, 768));  
    janela.setContentPane(painel);  
    painel.setLayout(null);  
    painelBonus = new PainelBonus();  
    painelBonus.setBounds(199, 537, 352, 156);  
    painel.add(painelBonus);  

    painelVida = new PainelVida();
    painelVida.setBounds(856, 426, 73, 267);
    //painelVida.setBounds();
    painel.add(painelVida);

    lblPontuacao = new JLabel("Pontua\u00E7\u00E3o: 0");
    lblPontuacao.setForeground(new Color(255, 69, 0));
    lblPontuacao.setBounds(0, 0, 1024, 22);
    lblPontuacao.setBackground(new Color(128, 0, 0));
    lblPontuacao.setOpaque(true);
    lblPontuacao.setHorizontalAlignment(SwingConstants.CENTER);
    painel.add(lblPontuacao);

    JLabel labelEsq = new JLabel("");
    labelEsq.setBackground(new Color(128, 0, 0));
    labelEsq.setOpaque(true);
    labelEsq.setBounds(0, 21, 11, 747);
    painel.add(labelEsq);

    GridPanel gridPanel_1 = new GridPanel();
    gridPanel_1.setBounds(10, 33, 767, 418);
    gridPanel_1.setShowGridLines(true);
    gridPanel_1.setRowSize(40);
    gridPanel_1.setColumnSize(40);
    gridPanel_1.setColumns(18);
    painel.add(gridPanel_1);

    JLabel labelDir = new JLabel("");
    labelDir.setOpaque(true);
    labelDir.setBackground(new Color(128, 0, 0));
    labelDir.setBounds(1013, 21, 11, 747);
    painel.add(labelDir);
}

This code painelBonus = new PainelBonus(); executes the constructor PainelBonus with all the components:

public PainelBonus() {  
    super();  
    painel = new JPanel();  
    painel.setBackground(new Color(0, 0, 0));  
    painel.setBorder(null);  
    painel.setPreferredSize(new Dimension(300, 157));  
    painel.setLayout(null);  

    imagemMartelo = new ImageIcon(PainelBonus.class.getResource("/Imagens/bonus/bonus_martelo/bonus_martelo_0.png"));
    imagemBomba = new ImageIcon(PainelBonus.class.getResource("/Imagens/bonus/bonus_bomba/bonus_bomba_0.png"));

    JButton btnImagemMartelo = new JButton("");
    btnImagemMartelo.setBounds(10, 11, 136, 136);
    btnImagemMartelo.setIcon(imagemMartelo);
    btnImagemMartelo.setContentAreaFilled(false);
    painel.add(btnImagemMartelo);

    JButton btnImagemBomba = new JButton("");
    btnImagemBomba.setBounds(154, 11, 136, 136);
    btnImagemBomba.setIcon(imagemBomba);
    btnImagemBomba.setContentAreaFilled(false);
    painel.add(btnImagemBomba);
}

Here's the problem: the components from PainelBonus doesn't seem to appear on PainelPrincipal

Screenshot: http://imgur.com/2wdZAOW

Sorry for bad formatting, kinda new here :D
TY Hovercraft Full Of Eels for the help on editing :D

回答1:

PainelBonus, which seems to extend from JPanel (or some other Component based class) creates it's own JPanel (painel = new JPanel();) to which you add some components, but you never add that panel (painel) to PainelBonus

Equally, PainelPrincipal creates a JPanel, painel onto which you add other components, including PainelBonus but this panel (painel) is never added to anything.

Don't use null layouts. Pixel perfect layouts are an illusion in modern UI design, you have no control over fonts, DPI, rendering pipelines or other factors that will change the way that you components will be rendered on the screen.

Swing was designed to work with layout managers to overcome these issues. If you insist on ignoring these features and work against the API design, be prepared for a lot of headaches and never ending hard work...

Updated with an example

public PainelPrincipal(Jogo janela) {`  
    super();  
    painel = new JPanel(){  
        protected void paintComponent(java.awt.Graphics g) { 
            super.paintComponents(g); 
            try{  
                // You shouldn't be loading resources in the paint method
                // And infact, this could be achieved by using a JLabel instead
                // of creating a custom JPanel
                g.drawImage(ImageIO.read(PainelPrincipal.class.getResource("Imagens/fundo/Fundo0.jpg")), 0, 0, this);  
            }catch(IOException e){  
                e.printStackTrace();  
            } 
        };
    };  
    //...
    setLayout(new BorderLayout());
    add(painel);
}

public PainelBonus() {  
    super();  
    setBackground(new Color(0, 0, 0));  
    setBorder(null);  
    setPreferredSize(new Dimension(300, 157));  
    setLayout(null);  

    imagemMartelo = new ImageIcon(PainelBonus.class.getResource("/Imagens/bonus/bonus_martelo/bonus_martelo_0.png"));
    imagemBomba = new ImageIcon(PainelBonus.class.getResource("/Imagens/bonus/bonus_bomba/bonus_bomba_0.png"));

    JButton btnImagemMartelo = new JButton("");
    btnImagemMartelo.setBounds(10, 11, 136, 136);
    btnImagemMartelo.setIcon(imagemMartelo);
    btnImagemMartelo.setContentAreaFilled(false);
    add(btnImagemMartelo);

    JButton btnImagemBomba = new JButton("");
    btnImagemBomba.setBounds(154, 11, 136, 136);
    btnImagemBomba.setIcon(imagemBomba);
    btnImagemBomba.setContentAreaFilled(false);
    add(btnImagemBomba);
}