blocks|key|917098|text|在你的班级里，你应该有：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|917099|public+void+paint(Graphics+g){
+++g.drawLine(x1,+y1,+x2,+y2);
}|code-block|syntax|javascript|917100|然后在代码中，如果需要，您将更改x1、y1、x2、y2并调用repaint();。|offset|length|style|CODE|917101|entityMap^0|0|0|U|A|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

In your class you should have:

<pre><code>public void paint(Graphics g){
 g.drawLine(x1, y1, x2, y2);
}
</code></pre>

Then in code if there is needed you will change x1, y1, x2, y2 and call <code>repaint();</code>.

blocks|key|701029|text|我知道您正在使用Java+AWT+API进行绘图。当控件需要重新绘制时，调用paint方法。我很确定它在Graphics参数中提供了哪个矩形需要重新绘制(以避免全部重新绘制)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|701030|因此，如果您呈现的是固定图像，则只需在该方法中绘制所需的任何内容。|701031|如果你是动画，我假设你可以使某些区域无效，并且paint方法将被自动调用。所以你可以修改状态，调用无效，然后它会被再次调用。|701032|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

I understand you are using Java AWT API for drawing. The paint method is invoked when the control needs repainting. And I'm pretty sure it provides in the Graphics argument what rectangle is the one who needs repainting (to avoid redrawing all).

So if you are presenting a fixed image you just draw whatever you need in that method.

If you are animating I assume you can invalidate some region and the paint method will be invoked automagically. So you can modify state, call invalidate, and it will be called again.

blocks|key|701084|text|可以使用要在其上绘制的组件的getGraphics方法。这反过来应该允许您绘制线条，并创建可通过Graphics类使用的其他内容|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|701085|entityMap|0|LINK|mutability|MUTABLE|url|http://download.oracle.com/javase/1.4.2/docs/api/java/awt/Component.html#getGraphics%2528%2529|1|http://download.oracle.com/javase/1.4.2/docs/api/java/awt/Graphics.html^0|E|B|0|1C|8|1|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]|$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]]]

You can use the <a href="http://download.oracle.com/javase/1.4.2/docs/api/java/awt/Component.html#getGraphics%28%29" rel="nofollow">getGraphics</a> method of the component on which you would like to draw. This in turn should allow you to draw lines and make other things which are available through the <a href="http://download.oracle.com/javase/1.4.2/docs/api/java/awt/Graphics.html" rel="nofollow">Graphics</a> class

blocks|key|917251|text|让我给你一些想法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|917252|public+void+paint(Graphics+g)+{
+++drawCoordinates(g);
}

private+void+drawCoordinates(Graphics+g)+{

++//+get+width+&+height+here+(w,h)

++//+define+grid+width+(dh,+dv)

++for+(int+x+=+0;+i+<+w;+i+%2B=+dh)+{
++++g.drawLine(x,+0,+x,+h);
++}
++for+(int+y+=+0;+j+<+h;+j+%2B=+dv)+{
++++++g.drawLine(0,+y,+w,+y);
++}
}|code-block|syntax|javascript|917253|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

To give you some idea:

<pre><code>public void paint(Graphics g) {
 drawCoordinates(g);
}

private void drawCoordinates(Graphics g) {

 // get width &amp; height here (w,h)

 // define grid width (dh, dv)

 for (int x = 0; i &lt; w; i += dh) {
 g.drawLine(x, 0, x, h);
 }
 for (int y = 0; j &lt; h; j += dv) {
 g.drawLine(0, y, w, y);
 }
}
</code></pre>

blocks|key|701161|text|您需要创建一个扩展Component的类。在那里，您可以覆盖paint方法并将您的绘制代码放入：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|701162|package+blah.whatever;

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

public+class+TestAWT+extends+Component+{

/**+@see+java.awt.Component#paint(java.awt.Graphics)+*/
@Override
public+void+paint(Graphics+g)+{
++++super.paint(g);
++++g.drawLine(0,0,100,100);
++++g.drawLine(10,+10,+20,+300);
++++//+more+drawing+code+here...
}

}|code-block|syntax|javascript|701163|将此组件放入应用程序的GUI中。如果您使用的是Swing，则需要扩展JComponent并覆盖paintComponent。|701164|正如Helios所提到的，绘制代码实际上告诉系统您的组件是什么样子的。当系统认为需要(重新)绘制时，系统将询问此信息(调用您的绘制代码)，例如，如果一个窗口移动到您的组件前面。|701165|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You need to create a class that extends Component. There you can override the paint method and put your painting code in:

<pre><code>package blah.whatever;

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

public class TestAWT extends Component {

/** @see java.awt.Component#paint(java.awt.Graphics) */
@Override
public void paint(Graphics g) {
 super.paint(g);
 g.drawLine(0,0,100,100);
 g.drawLine(10, 10, 20, 300);
 // more drawing code here...
}

}
</code></pre>

Put this component into the GUI of your application. If you're using Swing, you need to extend JComponent and override paintComponent, instead.

As Helios mentioned, the painting code actually tells the system how your component looks like. The system will ask for this information (call your painting code) when it thinks it needs to be (re)painted, for example, if a window is moved in front of your component.

blocks|key|701191|text|一个用于绘制线条的swing组件的非常简单的示例。它在内部保留了一个列表，其中包含使用addLine方法添加的行。每次添加新行时，都会调用重新绘制来通知图形子系统需要新的绘制。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|701192|这个类还包括一些用法示例。|701193|import+java.awt.BorderLayout;
import+java.awt.Color;
import+java.awt.Dimension;
import+java.awt.Graphics;
import+java.awt.event.ActionEvent;
import+java.awt.event.ActionListener;
import+java.util.LinkedList;

import+javax.swing.JButton;
import+javax.swing.JComponent;
import+javax.swing.JFrame;
import+javax.swing.JPanel;

public+class+LinesComponent+extends+JComponent{

private+static+class+Line{
++++final+int+x1;+
++++final+int+y1;
++++final+int+x2;
++++final+int+y2;+++
++++final+Color+color;

++++public+Line(int+x1,+int+y1,+int+x2,+int+y2,+Color+color)+{
++++++++this.x1+=+x1;
++++++++this.y1+=+y1;
++++++++this.x2+=+x2;
++++++++this.y2+=+y2;
++++++++this.color+=+color;
++++}+++++++++++++++
}

private+final+LinkedList<Line>+lines+=+new+LinkedList<Line>();

public+void+addLine(int+x1,+int+x2,+int+x3,+int+x4)+{
++++addLine(x1,+x2,+x3,+x4,+Color.black);
}

public+void+addLine(int+x1,+int+x2,+int+x3,+int+x4,+Color+color)+{
++++lines.add(new+Line(x1,x2,x3,x4,+color));++++++++
++++repaint();
}

public+void+clearLines()+{
++++lines.clear();
++++repaint();
}

@Override
protected+void+paintComponent(Graphics+g)+{
++++super.paintComponent(g);
++++for+(Line+line+:+lines)+{
++++++++g.setColor(line.color);
++++++++g.drawLine(line.x1,+line.y1,+line.x2,+line.y2);
++++}
}

public+static+void+main(String[]+args)+{
++++JFrame+testFrame+=+new+JFrame();
++++testFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
++++final+LinesComponent+comp+=+new+LinesComponent();
++++comp.setPreferredSize(new+Dimension(320,+200));
++++testFrame.getContentPane().add(comp,+BorderLayout.CENTER);
++++JPanel+buttonsPanel+=+new+JPanel();
++++JButton+newLineButton+=+new+JButton("New+Line");
++++JButton+clearButton+=+new+JButton("Clear");
++++buttonsPanel.add(newLineButton);
++++buttonsPanel.add(clearButton);
++++testFrame.getContentPane().add(buttonsPanel,+BorderLayout.SOUTH);
++++newLineButton.addActionListener(new+ActionListener()+{

++++++++@Override
++++++++public+void+actionPerformed(ActionEvent+e)+{
++++++++++++int+x1+=+(int)+(Math.random()*320);
++++++++++++int+x2+=+(int)+(Math.random()*320);
++++++++++++int+y1+=+(int)+(Math.random()*200);
++++++++++++int+y2+=+(int)+(Math.random()*200);
++++++++++++Color+randomColor+=+new+Color((float)Math.random(),+(float)Math.random(),+(float)Math.random());
++++++++++++comp.addLine(x1,+y1,+x2,+y2,+randomColor);
++++++++}
++++});
++++clearButton.addActionListener(new+ActionListener()+{

++++++++@Override
++++++++public+void+actionPerformed(ActionEvent+e)+{
++++++++++++comp.clearLines();
++++++++}
++++});
++++testFrame.pack();
++++testFrame.setVisible(true);
}

}|code-block|syntax|javascript|701194|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

A very simple example of a swing component to draw lines. It keeps internally a list with the lines that have been added with the method addLine. Each time a new line is added, repaint is invoked to inform the graphical subsytem that a new paint is required.

The class also includes some example of usage.

<pre><code>import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.LinkedList;

import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class LinesComponent extends JComponent{

private static class Line{
 final int x1; 
 final int y1;
 final int x2;
 final int y2; 
 final Color color;

 public Line(int x1, int y1, int x2, int y2, Color color) {
 this.x1 = x1;
 this.y1 = y1;
 this.x2 = x2;
 this.y2 = y2;
 this.color = color;
 } 
}

private final LinkedList&lt;Line&gt; lines = new LinkedList&lt;Line&gt;();

public void addLine(int x1, int x2, int x3, int x4) {
 addLine(x1, x2, x3, x4, Color.black);
}

public void addLine(int x1, int x2, int x3, int x4, Color color) {
 lines.add(new Line(x1,x2,x3,x4, color)); 
 repaint();
}

public void clearLines() {
 lines.clear();
 repaint();
}

@Override
protected void paintComponent(Graphics g) {
 super.paintComponent(g);
 for (Line line : lines) {
 g.setColor(line.color);
 g.drawLine(line.x1, line.y1, line.x2, line.y2);
 }
}

public static void main(String[] args) {
 JFrame testFrame = new JFrame();
 testFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
 final LinesComponent comp = new LinesComponent();
 comp.setPreferredSize(new Dimension(320, 200));
 testFrame.getContentPane().add(comp, BorderLayout.CENTER);
 JPanel buttonsPanel = new JPanel();
 JButton newLineButton = new JButton("New Line");
 JButton clearButton = new JButton("Clear");
 buttonsPanel.add(newLineButton);
 buttonsPanel.add(clearButton);
 testFrame.getContentPane().add(buttonsPanel, BorderLayout.SOUTH);
 newLineButton.addActionListener(new ActionListener() {

 @Override
 public void actionPerformed(ActionEvent e) {
 int x1 = (int) (Math.random()*320);
 int x2 = (int) (Math.random()*320);
 int y1 = (int) (Math.random()*200);
 int y2 = (int) (Math.random()*200);
 Color randomColor = new Color((float)Math.random(), (float)Math.random(), (float)Math.random());
 comp.addLine(x1, y1, x2, y2, randomColor);
 }
 });
 clearButton.addActionListener(new ActionListener() {

 @Override
 public void actionPerformed(ActionEvent e) {
 comp.clearLines();
 }
 });
 testFrame.pack();
 testFrame.setVisible(true);
}

}
</code></pre>

blocks|key|917466|text|我构建了一个完整的方法类来绘制点、线、矩形、圆等。我将其设计为将窗口视为一张图形纸，其中原点不必位于左上角，y值随着向上增加而增加。下面是我画线条的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|917467|public+static+void+drawLine+(double+x1,+double+y1,+double+x2,+double+y2)
{+++++++
++++((Graphics2D)g).draw(new+Line2D.Double(x0%2Bx1*scale,+y0-y1*scale,+x0%2Bx2*scale,+y0-y2*scale));
}|code-block|syntax|javascript|917468|在上面的示例中，(x0,+y0)表示屏幕坐标中的原点，scale是缩放因子。输入参数将作为图形坐标提供，而不是屏幕坐标。没有正在调用的repaint()。你可以保存它，直到你画完所有你需要的线条。|offset|length|style|CODE|917469|我突然想到，有些人可能不想用图表纸来思考：|917470|++++((Graphics2D)g).draw(new+Line2D.Double(x1,+y1,+x2,+y2));|917471|注意Graphics2D的用法。这允许我们使用doubles而不是int来绘制Line2D对象。除了其他形状之外，我的类还支持3D透视图和几种方便的方法(比如在给定半径的某个点上画一个圆)。如果有人感兴趣，我很乐意分享更多这门课的内容。|917472|entityMap^0|0|0|8|8|R|5|1V|9|0|0|0|2|A|13|6|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]|$I|Z|J|10|K|L]|$I|11|J|12|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|15|8|@$I|16|J|17|K|L]|$I|18|J|19|K|L]]|9|@]|A|$]]|$1|S|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|T|$]]

I built a whole class of methods to draw points, lines, rectangles, circles, etc. I designed it to treat the window as a piece of graph paper where the origin doesn't have to be at the top left and the y values increase as you go up. Here's how I draw lines:

<pre><code>public static void drawLine (double x1, double y1, double x2, double y2)
{ 
 ((Graphics2D)g).draw(new Line2D.Double(x0+x1*scale, y0-y1*scale, x0+x2*scale, y0-y2*scale));
}
</code></pre>

In the example above, <code>(x0, y0)</code> represents the origin in screen coordinates and <code>scale</code> is a scaling factor. The input parameters are to be supplied as graph coordinates, not screen coordinates. There is no <code>repaint()</code> being called. You can save that til you've drawn all the lines you need.

It occurs to me that someone might not want to think in terms of graph paper:

<pre><code> ((Graphics2D)g).draw(new Line2D.Double(x1, y1, x2, y2));
</code></pre>

Notice the use of <code>Graphics2D</code>. This allows us to draw a <code>Line2D</code> object using doubles instead of ints. Besides other shapes, my class has support for 3D perspective drawing and several convenience methods (like drawing a circle centered at a certain point given a radius.) If anyone is interested, I would be happy to share more of this class.

blocks|key|701324|text|要回答您最初的问题，可以使用(x1,+y1)+To+(x2,+y2)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|701325|例如,|701326|这是为了画一条水平线：|701327|g.drawLine(+10,+30,+90,+30+);|code-block|syntax|javascript|701328|vs|701329|这是为了画一条垂直线：|701330|g.drawLine(+10,+30,+10,+90+);|701331|我希望它能帮上忙。|701332|entityMap^0|E|8|Q|8|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|13|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|14|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|15|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|16|8|@]|D|@]|E|$]]|$1|Q|3|R|5|6|7|17|8|@]|D|@]|E|$]]|$1|S|3|T|5|L|7|18|8|@]|D|@]|E|$M|N]]|$1|U|3|V|5|6|7|19|8|@]|D|@]|E|$]]|$1|W|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|X|$]]

To answer your original question, it's <code>(x1, y1)</code> to <code>(x2, y2)</code>.

For example, 

This is to draw a horizontal line:

<pre><code>g.drawLine( 10, 30, 90, 30 );
</code></pre>

vs

This is to draw a vertical line:

<pre><code>g.drawLine( 10, 30, 10, 90 );
</code></pre>

I hope it helps.

blocks|key|917536|text|a+simple+line+,+after+that+you+can+see+also+a+doted+line+

import+java.awt.*;

import+javax.swing.*;

import+java.awt.Graphics.*;

import+java.awt.Graphics2D.*;

import+javax.swing.JFrame;

import+javax.swing.JPanel;

import+java.awt.BasicStroke;

import+java.awt.Event.*;

import+java.awt.Component.*;

import+javax.swing.SwingUtilities;


/**
+*
+*+@author+junaid
+*/
public+class+JunaidLine+extends+JPanel{


//private+Graphics+Graphics;

private+void+doDrawing(Graphics+g){

Graphics2D+g2d=(Graphics2D)+g;

float[]+dash1+=+{2f,0f,2f};

g2d.drawLine(20,+40,+250,+40);

BasicStroke+bs1+=+new+BasicStroke(1,BasicStroke.CAP_BUTT,

++++++++++++++++++++BasicStroke.JOIN_ROUND,1.0f,dash1,2f);

g2d.setStroke(bs1);

g2d.drawLine(20,+80,+250,+80);

++++}

@Override

public+void+paintComponent(Graphics+g){

super.paintComponent(+g);

doDrawing(g);

}


}

class+BasicStrokes+extends+JFrame{

public++BasicStrokes(){

initUI();

}

private+void+initUI(){

setTitle("line");

setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

add(new+JunaidLine());

setSize(280,270);

setLocationRelativeTo(null);

}

/**

*+@param+args+the+command+line+arguments

*/

public+static+void+main(String[]+args)+{


SwingUtilities.invokeLater(new+Runnable(){+++

@Override

public+void+run(){

BasicStrokes+bs+=+new+BasicStrokes();

bs.setVisible(true);

}++++++++++++++++

});

}


}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|917537|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>a simple line , after that you can see also a doted line 

import java.awt.*;

import javax.swing.*;

import java.awt.Graphics.*;

import java.awt.Graphics2D.*;

import javax.swing.JFrame;

import javax.swing.JPanel;

import java.awt.BasicStroke;

import java.awt.Event.*;

import java.awt.Component.*;

import javax.swing.SwingUtilities;


/**
 *
 * @author junaid
 */
public class JunaidLine extends JPanel{


//private Graphics Graphics;

private void doDrawing(Graphics g){

Graphics2D g2d=(Graphics2D) g;

float[] dash1 = {2f,0f,2f};

g2d.drawLine(20, 40, 250, 40);

BasicStroke bs1 = new BasicStroke(1,BasicStroke.CAP_BUTT,

 BasicStroke.JOIN_ROUND,1.0f,dash1,2f);

g2d.setStroke(bs1);

g2d.drawLine(20, 80, 250, 80);

 }

@Override

public void paintComponent(Graphics g){

super.paintComponent( g);

doDrawing(g);

}


}

class BasicStrokes extends JFrame{

public BasicStrokes(){

initUI();

}

private void initUI(){

setTitle("line");

setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

add(new JunaidLine());

setSize(280,270);

setLocationRelativeTo(null);

}

/**

* @param args the command line arguments

*/

public static void main(String[] args) {


SwingUtilities.invokeLater(new Runnable(){ 

@Override

public void run(){

BasicStrokes bs = new BasicStrokes();

bs.setVisible(true);

} 

});

}


}
</code></pre>

I'm wondering if there's a funciton in Java that can draw a line from the coordinates (x1, x2) to (y1, y2)?

What I want is to do something like this:

<pre><code>drawLine(x1, x2, x3, x4);
</code></pre>

And I want to be able to do it at any time in the code, making several lines appear at once.

I have tried to do this:

<pre><code>public void paint(Graphics g){
 g.drawLine(0, 0, 100, 100);
}
</code></pre>

But this gives me no control of when the function is used and I can't figure out how to call it several times.

Hope you understand what I mean!

P.S. I want to create a coordinate system with many coordinates.

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