如何在另一个方法中使用返回语句？

Question

我想通过将它传递给showWindow来调用load_picture中的return语句tempimage，但我不知道如何。继承人我的代码片段。编辑： 我想我想说的是，我不完全确定如何处理硬编码“picture1.gif”。我知道我需要调用一个方法来加载图像，但我不太清楚应该放置什么。 ：

package project3; 

import java.util.Scanner; 
import javax.swing.; 
import java.awt.; 
import java.net.*; 

public class Project3 { 
    //initializing global 
static Project3 theobject = new Project3(); 
final static int MIN_NUMBER=1; 
final static int MAX_NUMBER=8; 
static int image_number=1; 
static Image theimage; 
// This routine will load an image into memory, non-static requires an object 
// It expects the name of the image file name and a JFrame passed to it 
// It will assume an Internet conection is available 
// It can only be called AFTER the program object has been created 
// It will return a type Image variable, call it like this: theimage = object.load_picture("picture1.gif", frame); 
// (hard code 'picture1.gif' only when testing - USE a method or variable for 'real' call) 
// This code requires you to do an 'import java.awt.*' and an 'import java.net.*' 
// Note: this method is using parameter and return type for input/output 

// This routine will load an image into memory, non-static requires an object 
// It expects the name of the image file name and a JFrame passed to it 
// It will assume an Internet conection is available 
// It can only be called AFTER the program object has been created 
// It will return a type Image variable, call it like this: theimage = object.load_picture("picture1.gif", frame); 
// (hard code 'picture1.gif' only when testing - USE a method or variable for 'real' call) 
// This code requires you to do an 'import java.awt.*' and an 'import java.net.*' 
// Note: this method is using parameter and return type for input/output 

public Image load_picture(String imagefile, JFrame theframe) 
{ 

Image tempimage; 
// Create a MediaTracker to inform us when the image has 
// been completely loaded. 
MediaTracker tracker; 
tracker = new MediaTracker(theframe); 

// getImage() returns immediately. The image is not 
// actually loaded until it is first used. We use a 
// MediaTracker to make sure the image is loaded 
// before we try to display it. 

String startURL; 
if (imagefile.startsWith("http")) 
    startURL = ""; 
else 
    startURL = "http://www.canyons.edu/departments/comp_sci/ferguson/cs111/images/"; 

URL myURL=null; 
try 
{ 
myURL = new URL(startURL + imagefile); 
} 
catch(MalformedURLException e) { 
    System.out.println("Error caught " + e.toString()); 
} 

//tempimage = getImage(myURL); // JApplet version 
tempimage = Toolkit.getDefaultToolkit().getImage(myURL); // stand alone program version 


// Add the image to the MediaTracker so that we can wait for it 

tracker.addImage(tempimage, 0); 
try { tracker.waitForID(0); } 
catch (InterruptedException err) { System.err.println(err); } 

return tempimage; 
} 

// This class/method uses a global variable that MUST be set before calling/using 
// note: You can not call the paint routine directly, it is called when frame/window is shown 
// look up the repaint() routine in the book 
// Review Listings 8.5 and 8.6 
// 
public static class MyPanel extends JPanel { 
public void paintComponent (Graphics g) { 
    JPanel panel= new JPanel(); 
    int xpos,ypos; 
    super.paintComponent(g); 
    // set the xpos and ypos before you display the image 
    xpos = 300; // you pick the position 
    ypos = 200; // you pick the position 
    if (theimage != null) { 
     g.drawImage(theimage,xpos,ypos,this); 
     // note: theimage global variable must be set BEFORE paint is called 
    } 
} 
} 
public static void showWindow(String filename) { 
    // create, size and show a GUI window frame, you may need to click on taskbar to see window 
    //display the filename in the title of the window frame, otherwise the window will be blank (for now) 

JFrame frame1= new JFrame(); 
theimage = theobject.load_picture("picture1.gif", frame1); 
//"picture1.gif" is hardcoded, I want to call this using a method 
frame1.setTitle(filename); 
frame1.setSize(440,302); 
frame1.setLocation(400,302); 
frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
frame1.setVisible(true); 
} 

任何帮助表示赞赏。由于

Answer 1

从的ShowWindow方法中，只需调用load_picture方法如下：

Image tempImage = load_picture(filename, frame1); 

从这里你可以做任何你与tempImage对象喜欢。

Answer 2

由该load_picture方法返回的值可以直接发送到showWindow方法，也可以将其分配给一个变量：

String filename = "your/filename"; 
JFrame theFrame = new JFrame(); 
Project3 project = new Project3(); 
MyPanel.showWindow(project.load_picture(filename, theFrame);