getGraphics() によりゲームが起動できなくなります [終了]

StackOverflow https://stackoverflow.com//questions/12656661

  •  11-12-2019
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質問

私はダブルバッファリングについて学んでいますが、先生からもらった本には、書いたことを書くように書かれています。しかし、Java が画像からグラフィックス オブジェクトを取得しようとするとクラッシュします。

フレーム = 画像
エンジン＝グラフィックス

エラー

Exception in thread "main" java.lang.NullPointerException
at Engine.<init>(Engine.java:30)
at Game.<init>(Game.java:35)
at Game.main(Game.java:22)

Image 1

Image 2

ゲーム.java

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import javax.swing.*;
import java.util.*;
import java.util.Timer;

public class Game implements ActionListener {

private static Game hosmos2;
private JFrame frmMain;
private AntiCheat holyanticheat;
private Dimension screen;
private Engine holyengine;
private int sx, sy;
private Timer timCheat;

public static void main(String[] args) throws FileNotFoundException, InterruptedException {

    hosmos2 = new Game();
}

private Game() throws FileNotFoundException, InterruptedException {

    frmMain = new JFrame("Hosmos 2");
    frmMain.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frmMain.setSize(1366, 768);
    screen = Toolkit.getDefaultToolkit().getScreenSize();
    sx = (int) ((screen.getWidth() - frmMain.getWidth()) / 2);
    sy = (int) ((screen.getHeight() - frmMain.getHeight()) / 2);
    frmMain.setLocation(sx, sy);
    holyanticheat = new AntiCheat();
    holyengine = new Engine();
    timCheat = new Timer();
    frmMain.setVisible(true);
    timCheat.schedule(holyanticheat, 500);
    Thread.sleep(1000);
    timCheat.cancel();
}

public void actionPerformed(ActionEvent e) {


}

}

エンジン.java

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import javax.swing.*;
import java.util.*;

public class Engine extends JPanel {

private boolean countdown, quality;
private Font text, text2;
private Graphics engine;
private Image frame;
private ImageIcon background, button1, button21, button22, button3, button4, button51, button52, header;
private int weedbackground, fps, fps2;
public Rectangle box1, box2, box3, box4, box5;

public static void main(String[] args) {


}

public Engine() {

    this.setBackground(Color.black);
    frame = createImage(getSize().width, getSize().height);
    text = new Font("Microsoft Sans Serif", Font.BOLD, 24);
    text2 = new Font("Microsoft Sans Serif", Font.BOLD, 8);
    engine = frame.getGraphics(); // Error
    background = new ImageIcon("textures/background.png");
    //background = background.GetThumbnailImage(source.ClientSize.Width, source.ClientSize.Height, null, IntPtr.Zero);
    button1 = new ImageIcon("textures/button 1.png");
    button21 = new ImageIcon("textures/button 2-1.png");
    button22 = new ImageIcon("textures/button 2-2.png");
    button3 = new ImageIcon("textures/button 3.png");
    button4 = new ImageIcon("textures/button 4.png");
    button51 = new ImageIcon("textures/button 5-1.png");
    button52 = new ImageIcon("textures/button 5-2.png");
    header = new ImageIcon("textures/header.png");
    box1 = new Rectangle(20, 20, 87, 37);
    box2 = new Rectangle(20, 60, 96, 37);
    box3 = new Rectangle(20, 103, 182, 43);
    box4 = new Rectangle(20, 146, 83, 43);
    box5 = new Rectangle(20, 189, 206, 43);
}

public Rectangle GetBox1() {

    return box1;
}

public Rectangle GetBox2() {

    return box2;
}

public Rectangle GetBox3() {

    return box3;
}

public Rectangle GetBox4() {

    return box4;
}

public Rectangle GetBox5() {

    return box5;
}

public void FPS()
{
    fps2 = fps;
    fps = 0;
}

public void Quality(boolean quality2)
{
    quality = quality2;
}

public void Render(boolean music, boolean effect, int time, int spawned, int points, int cracktime, int crackend, int shieldtime, int shieldend, int weedtime, int weedend, ImageIcon malcolm, int malcolmX, int malcolmY, int item, ImageIcon crack, int crackX, int crackY, ImageIcon nuke, int nukeX, int nukeY, ImageIcon shield, int shieldX, int shieldY, ImageIcon skull, int skullX, int skullY, ImageIcon trollface, int trollfaceX, int trollfaceY, ImageIcon weed, int weedX, int weedY, LinkedList<Hosmin> hosmins) {

    engine = frame.getGraphics();
    super.paintComponent(engine);
    if (effect == false) {

        if (quality == false) {

            background.paintIcon(this, engine, 0, 0);
        }
        else {

            this.setBackground(Color.black);
        }
    }
    else {

        if (weedbackground == 1) {

            this.setBackground(Color.green);
            weedbackground++;
        }
        else if (weedbackground == 2) {

            this.setBackground(Color.yellow);
            weedbackground++;
        }
        else if (weedbackground == 3) {

            this.setBackground(Color.red);
            weedbackground = 1;
        }
    }
    header.paintIcon(this, engine, 547, 10);
    button1.paintIcon(this, engine, 20, 20);
    if (music == false) {

        button21.paintIcon(this, engine, 20, 60);
    }
    else {

        button22.paintIcon(this, engine, 20, 60);
    }
    button3.paintIcon(this, engine, 20, 103);
    button4.paintIcon(this, engine, 20, 146);
    if (quality == false) {

        button51.paintIcon(this, engine, 20, 189);
    }
    else {

        button52.paintIcon(this, engine, 20, 189);
    }
    engine.setFont(text2);
    engine.setColor(Color.green);
    engine.drawString("FPS: " + fps2, 1293, 9);
    engine.setFont(text);
    engine.setColor(Color.red);
    engine.drawString("Time: " + time, 1178, 22);
    engine.drawString("Hosmins: " + spawned, 1124, 59);
    engine.drawString("Points: " + points, 1160, 96);
    engine.setFont(text2);
    engine.setColor(Color.green);
    engine.drawString("Developer: HolyDuFF", 1229, 708);
    malcolm.paintIcon(this, engine, malcolmX, malcolmY);
    if (countdown == true) {

        if (crackend - cracktime == 0) {

            countdown = false;
        }
        else if (cracktime >= 0) {

            engine.setFont(text);
            engine.setColor(Color.red);
            crackend = crackend - cracktime;
            if (crackend != 10) {

                engine.drawString("" + crackend, malcolmX + 17, malcolmY - 40);
            }
            else {

                engine.drawString("" + crackend, malcolmX + 7, malcolmY - 40);
            }
        }
        else if (shieldtime >= 0) {

            engine.setFont(text);
            engine.setColor(Color.red);
            shieldend = shieldend - shieldtime;
            if (shieldend != 10) {

                engine.drawString("" + shieldend, malcolmX + 17, malcolmY - 40);
            }
            else {

                engine.drawString("" + shieldend, malcolmX + 7, malcolmY - 40);
            }
        }
        else if (weedtime >= 0) {

            engine.setFont(text);
            engine.setColor(Color.blue);
            weedend = weedend - weedtime;
            if (weedend != 10) {

                engine.drawString("" + weedend, malcolmX + 17, malcolmY - 40);
            }
            else {

                engine.drawString("" + weedend, malcolmX + 7, malcolmY - 40);
            }
        }
    }
    for (int i = 0; i < hosmins.size(); i++) {

        Hosmin temp = hosmins.get(i);
        temp.Draw().paintIcon(this, engine, temp.GetX(), temp.GetY());
    }
    if (item == 1) {

        crack.paintIcon(this, engine, crackX, crackY);
    }
    else if (item == 2) {

        nuke.paintIcon(this, engine, nukeX, nukeY);
    }
    else if (item == 3) {

        shield.paintIcon(this, engine, shieldX, shieldY);
    }
    else if (item == 4) {

        skull.paintIcon(this, engine, skullX, skullY);
    }
    else if (item == 5) {

        trollface.paintIcon(this, engine, trollfaceX, trollfaceY);
    }
    else if (item == 6) {

        weed.paintIcon(this, engine, weedX, weedY);
    }
    engine.dispose();
    repaint();
    fps++;
}

public void paintComponent(Graphics g) {

    super.paintComponent(g);
    g.drawImage(frame, 0, 0, this);
}

public void SetBackground(int background2) {

    weedbackground = background2;
}

public void SetCountdown(boolean countdown2) {

    countdown = countdown2;
}

public void SetBox2(int mode) {

    if (mode == 1) {

        box2.width = 96;
        box2.height = 37;
    }
    else {

        box2.width = 76;
        box2.height = 43;
    }
}

public void SetBox5(int mode) {

    if (mode == 1) {

        box5.width = 206;
    }
    else {

        box5.width = 213;
    }
}

}
役に立ちましたか？

解決

あなたが呼んでいます getGraphics() null の Image 変数の場合。コンポーネントの API を見ると、 createImage() これがなぜそうなるかはわかります。

ダブルバッファリングに使用できるオフスクリーン描画可能イメージを返します。 コンポーネントが表示できない場合、戻り値は null になる可能性があります. 。これは、GraphicsEnvironment.isHeadless() が true を返した場合に常に発生します。

エンジンはコンストラクターにまだ表示されていません。GUI は、最初に呼び出してレンダリングする必要があります。 pack() または setVisible(true) この JPanel が表示される前に、トップレベルのウィンドウに が表示されます。

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