Question

所以我试图创建一个使用两个JSliders来调整矩形大小的Applet。我希望从底部到顶部的高度与Vertical JSlider的外观相匹配。

我遇到的唯一问题是用Java绘制图纸来自x＆amp; y，它们都位于0，向左移动x（向西），y向南移动。调整宽度的大小很简单，因为我只使用带有单个参数的方法来增加或减少宽度。随着高度，向上移动是很好的（我已经设置为340，因为这是我想留下的基础）。当我向下移动JSlider时，它向下移动但不会达到它曾经的高度。我真的很想看看矩形的移动方式与JSlider的移动方式相同。

主Applet页面（JSliders所在的位置）：

import java.awt.BorderLayout;
import java.awt.Color;

import javax.swing.JApplet;
import javax.swing.JLabel;
import javax.swing.JSlider;
import javax.swing.SwingConstants;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;


public class ResizeRectangle extends JApplet {
    private JSlider sliderHeight;
    private JSlider sliderWidth;
    private JLabel title;
    private Contents content;
    private int oldValue = 0;
    public void init(){

        setLayout(new BorderLayout());

        title = new JLabel("Rectangle Resizer");
        content = new Contents();

        content.setBackground(Color.WHITE);

        //Slider for increasing the height
        sliderHeight = new JSlider(SwingConstants.VERTICAL, 10, 100, 10);
        sliderHeight.setMajorTickSpacing(10);
        sliderHeight.setPaintTicks(true);

        sliderHeight.addChangeListener(
                new ChangeListener(){
                    public void stateChanged(ChangeEvent e){
                        //If sliderHeight is greater than oldValue pass true for increase
                        if(sliderHeight.getValue() > oldValue){
                            content.setHeight(sliderHeight.getValue(), true);
                        }
                        //Else if sliderHeight is less than oldValue pass false for increase
                        else if(sliderHeight.getValue() < oldValue){
                            content.setHeight(sliderHeight.getValue(), false);
                        }
                        //Sets the value of sliderHeight to the value of oldValue to compare later
                        oldValue = sliderHeight.getValue();
                    }
                }
        );
        //Slider for increasing the widht
        sliderWidth = new JSlider(SwingConstants.HORIZONTAL, 10, 100, 10);
        sliderWidth.setMajorTickSpacing(10);
        sliderWidth.setPaintTicks(true);

        sliderWidth.addChangeListener(
                new ChangeListener(){
                    public void stateChanged(ChangeEvent e){
                        content.setWidth(sliderWidth.getValue());
                    }
                }
        );

        content.setBackground(Color.WHITE);
        add(title, BorderLayout.NORTH);
        add(content, BorderLayout.CENTER);
        add(sliderWidth, BorderLayout.SOUTH);
        add(sliderHeight, BorderLayout.EAST);

    }
}

这是设置高度（以及宽度）的代码：

import java.awt.Component;
import java.awt.Graphics;



public class Contents extends Component {

    private int height = 10;
    private int width = 10;
    //Initialize y to 340.
    private int y = 340;

    //Draw the rectangle
    public void paint(Graphics g){
        g.fillRect(5, y, width, height);
    }

    public void setHeight(int h, boolean increase){
        //If the slider is increasing, decrease y and increase height to give it the
        // look of rising 
        if(increase){
            y = y - h;
            height = height + h;
        }
        //else do the opposite
        else{
            y = y + h;
            height = height - h;
        }
        //For debugging purposes
        System.out.println("h = "+h);
        System.out.println("y = "+y);
        System.out.println("height = "+height+"\n\n");
        //Repaint the rectangle
        repaint();

    }
    //Set the width and repaint
    public void setWidth(int w){
        width = w;
        repaint();
    }
}

这是我学习Java的第三个月，我非常感谢任何反馈。提前谢谢。

Answer 1

您的代码存在逻辑问题。用于更改更改侦听器内部高度的调用是

content.setHeight(sliderHeight.getValue(), ...);

第一眼看上去很合理。然而，方法setHeight没有做出名称所暗示的（即设置高度），而是以第一个参数给出的量增加或减少高度：

if(increase){
    y = y - h;
    height = height + h;
} else {
    y = y + h;
    height = height - h;
}

因此，如果滑块从10更改为20并返回10，则您可以更改以下值：

// initial values
y = 340
height = 10     

// change from 10 to 20, thus h=20 and increase as arguments for the method
y -> 340 - 20 = 320
height -> 10 + 20 = 30


// change from 20 back to 10, i.e. h=10 and decrease
y -> 320 + 10 = 330
height -> 30 - 10 = 20

该方法应该做的事实是确定高度，即

y = 340 - h;
height = h;

如何从下到上动态调整矩形的大小。 Java的

1 个答案: