错误：
Exception in thread "main" java.lang.IllegalStateException: Component must have a valid peer
at java.awt.Component$FlipBufferStrategy.createBuffers(Component.java:3998)
at java.awt.Component$FlipBufferStrategy.<init>(Component.java:3972)
at java.awt.Component$FlipSubRegionBufferStrategy.<init>(Component.java:4495)
at java.awt.Component.createBufferStrategy(Component.java:3849)
at java.awt.Canvas.createBufferStrategy(Canvas.java:194)
at java.awt.Component.createBufferStrategy(Component.java:3773)
at java.awt.Canvas.createBufferStrategy(Canvas.java:169)
at KMap.draw(KMap.java:276)
at KMap.run(KMap.java:246)
at KMap.<init>(KMap.java:33)
at Driver.main(Driver.java:6)
我读了一些其他帖子说我必须将Canvas添加到我的JFrame中，但问题仍然存在。现在我只想显示黑屏。如果有人可以帮助我，我会很感激。感谢
完整代码:(滚动到问题的底部）
import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JFrame;
public class KMap extends Canvas
{
private ArrayList<String> variableNameList = new ArrayList<String>();
private String [] characters = {"A","B","C","D","E","F","G","H","I","J"};
private ArrayList<int[]> values = new ArrayList<int[]>();
private int[][] cell, leftValues, topValues;
private int leftValuesSize, topValuesSize;
private Canvas c = new Canvas();
private JFrame f;
public KMap(int i)
{
f = new JFrame();
f.setTitle("Karnaugh Map for COMP 228");
f.setLayout(new BorderLayout());
updateVariables(i);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
f.setResizable(false);
f.setLocationRelativeTo(null);
f.add(c);
run(i);
}
public void updateVariables(int numV)
{
/*
* The characters[] String array
* holds the first ten letters of the alphabet(Since
* the maximum number of variables can be 10). This loop
* adds the names of the variables that need to be stored
* inside 'variableNameList'. Example: if number of variables
* (numV) = 5, then variable name list consists of the first
* five Strings of characters[], "A", "B", "C", "D", "E".
*/
variableNameList.clear();
for(int i = 0; i < numV; i++)
variableNameList.add(characters[i]);
System.out.println();
/*
* The below for loop creates a list of all possible combinations between
* the variables. For example, if numV(number of variables
* is 5, the number of combinations will be 25). It will
* start from 0, ending at 24, and convert those integers
* to their binary values to store in the array list
* called 'values'. These binary values will be used
* as our truth table to help out with the K-Map (although
* the truth table will not be displayed).*/
int combinations = (int) Math.pow(2,numV);
System.out.println(combinations);
System.out.println("New variables: " + numV);
values.clear();
for(int i = 0; i < combinations; i++)
{
int binary[] = new int[numV];
if(i == 0)
for(int j = 0; j < numV; j++)
binary[j] = 0;
else
{
for(int z = 0; z < values.get(i-1).length; z++)
binary[z] = values.get(i-1)[z];
for(int a = numV-1; a >= 0; a--)
{
if(binary[a]==0)
{
binary[a]++;
break;
}
else
binary[a]=0;
}
}
values.add(binary);
for(int j = 0; j < values.get(i).length; j++)
System.out.print(values.get(i)[j]);
System.out.println();
}
createMapValues(numV);
}
public void createMapValues(int numV)
{
/*From the 'values' array list consisting of binary numbers
* (stored as int[] types), and a list of names for variables
* (within the 'variableNameList' array, topString will be the
* variable names on the top, and leftString will the names to the left
* Example: i have 5 variables. Top string = "ABC", left = "DE"
*
* For the top values "ABC" can be, it will pull a list of combinations
* from 'values'. In this case, since there are 3 values, it will pull out
* 2^3. So: 000,001,010,011,100,101,110,111. Then assign those values
* to the 2-D array for the top values, 'topValues[][]'. Same thing
* for the left values.
*
*/
String[] characterSet = new String[variableNameList.size()];
for(int i = 0; i < variableNameList.size(); i++)
characterSet[i] = variableNameList.get(i);
JButton emptyButton = new JButton();
String topString = "";
String leftString = "";
System.out.println(numV);
int topCount = numV/2;
int leftCount = numV-topCount;
System.out.println(topCount);
System.out.println(leftCount);
for(int i = 0; i < topCount; i++)
{
topString+=characterSet[i];
}
for(int i = topCount; i < numV; i++)
{
leftString+=characterSet[i];
}
topValuesSize = topString.length();
topValues = new int[(int) Math.pow(2, topString.length())][topValuesSize];
leftValuesSize = leftString.length();
leftValues = new int[(int) Math.pow(2, leftString.length())][leftValuesSize];
for(int i = 0; i < topValues.length; i++)
for(int j = 0; j < topValuesSize; j++)
topValues[i][j] = values.get(i)[numV-topValuesSize+j];
for(int i = 0; i < leftValues.length; i++)
for(int j = 0; j < leftValuesSize; j++)
leftValues[i][j] = values.get(i)[numV-leftValuesSize+j];
System.out.println(topString + "=");
for(int i = 0; i < topValues.length; i++)
{
for(int j = 0; j < topValuesSize; j++)
System.out.print(topValues[i][j]);
System.out.println();
}
System.out.println(leftString + "=");
for(int i = 0; i < leftValues.length; i++)
{
for(int j = 0; j < leftValuesSize; j++)
System.out.print(leftValues[i][j]);
System.out.println();
}
cell = new int[topValues.length][leftValues.length];
for(int i = 0; i < topValues.length; i++)
{
for(int j = 0; j < leftValues.length; j++)
cell[0][j] = 0;
}
}
private boolean running = false;
private long second = 1000000000;
private long fps = 60;
private long frame = second/fps;
private long frames = 0;
private long seconds = 0;
public void run(int numV)
{
long now = System.nanoTime();
long lastSecond = now;
long lastFrame = now;
long deltaSecond = now-lastSecond;
long deltaFrame = now-lastFrame;
running = true;
while(true)
{
while(running)
{
now = System.nanoTime();
deltaSecond = now-lastSecond;
deltaFrame = now-lastFrame;
if(deltaFrame>=frame)
{
draw(numV);
f.pack();
lastFrame = now;
frames++;
}
if(deltaSecond>=second)
{
lastSecond = now;
seconds++;
frames = 0;
}
}
}
}
public void draw(int numV)
{
/*
*
*/
int w = (leftValues.length + 2)*50;
int topH = 50;
int midH = (topValues.length + 2)*50;
int botH = 50;
int h = topH + midH + botH;
setSize(w, h);
BufferStrategy bs = getBufferStrategy();
if(bs==null)
{
createBufferStrategy(3);
return;
}
Graphics g = bs.getDrawGraphics();
g.setColor(Color.BLACK);
g.fillRect(0, 0, w, h);
g.dispose();
bs.show();
}
}
答案 0 :(得分：1)
在KMap构造函数中，不添加否则未使用的Canvas，添加此项并在运行之前将帧设置为可见。
public KMap(int i)
{
f = new JFrame();
f.setTitle("Karnaugh Map for COMP 228");
f.setLayout(new BorderLayout());
updateVariables(i);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
f.setResizable(false);
f.setLocationRelativeTo(null);
f.add(this);
f.setVisible(true);
run(i);
}