小编Car*_*aru的帖子

我有一个简单的类,当鼠标拖动时绘制一条线或鼠标按下(释放)时画一个点.

当我最小化应用程序然后恢复它时,窗口的内容消失,除了最后一个点(像素).我知道super.paint(g)每次窗口改变时该方法都会重新绘制背景,但无论我是否使用它,结果似乎都是一样的.它们之间的区别在于,当我不使用它时,窗口上绘制的不仅仅是一个像素,而不是我的所有绘画.我怎样才能解决这个问题？

这是班级.

package painting;

import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import javax.swing.JFrame;
import javax.swing.JPanel;

class CustomCanvas extends Canvas{   
    Point oldLocation= new Point(10, 10);
    Point location= new Point(10, 10);
    Dimension dimension = new Dimension(2, 2);     
    CustomCanvas(Dimension dimension){  
        this.dimension = dimension;   
        this.init();
        addListeners();
    }    
    private void init(){                     
        oldLocation= new Point(0, 0);
        location= new Point(0, 0);
    }
    public void paintLine(){
        if ((location.x!=oldLocation.x) || (location.y!=oldLocation.y)) {         
            repaint(location.x,location.y,1,1);                                   
        } 
    }
    private void addListeners(){
        addMouseListener(new MouseAdapter(){
            @Override
            public void mousePressed(MouseEvent me){ …

我正在尝试在java中签署一条消息,它似乎不起作用.验证步骤给了我错误.

谁能告诉我我的错误在哪里？我无法理解我做错了什么.谢谢

String messageString = "text";
try {
        KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA", "BC");
        keyGen.initialize(512, new SecureRandom());
        KeyPair keyPair = keyGen.generateKeyPair();
        PublicKey RSAPublicKey = keyPair.getPublic();
        PrivateKey RSAPrivateKey = keyPair.getPrivate();

        System.out.println("public key = " + RSAPublicKey);
        System.out.println("private key = " + RSAPrivateKey);

        Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
        Signature signature = Signature.getInstance("SHA1withRSA", "BC");
        signature.initSign(RSAPrivateKey, new SecureRandom());
        byte[] message = messageString.getBytes();
        signature.update(message);
        byte[] sigBytes = signature.sign();

        Signature signature1 = Signature.getInstance("SHA1withRSA", "BC");
        signature1.initVerify(RSAPublicKey);
        signature1.update(sigBytes);

        boolean result = signature1.verify(sigBytes);
        System.out.println("result = "+result);
    } catch (NoSuchAlgorithmException | NoSuchProviderException | SignatureException …