get（Object obj）of field not working with instance variables

Question

我很疑惑爲什麼get（Object obj）不能與實例變量（實例字段）一起工作，並拋出IllegalArgumentException。

我有以下類：

public class InfoSender { 

String testInt = "hey"; 

/** 
* @param args the command line arguments 
*/ 
public static void main(String[] args) { 
    InfoSender test = new InfoSender(); 
    test.asd(); 
    //  script g = new script(); 
    //  mobile h = new mobile(); 
} 

private void asd() { 
    new StatusGUI(this); 
} 

}

和我有StatusGUI類（不包括的initComponents）：

public class StatusGUI extends javax.swing.JFrame { 

Class clazz; 

/** Creates new form StatusGUI */ 
public StatusGUI(Object invokerObject) { 
    initComponents(); 
    setVisible(true); 
    setLocationRelativeTo(null); 
    clazz = invokerObject.getClass(); 
} 
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {           
    try { 
     Field[] fields = clazz.getDeclaredFields(); 
     for (int i = 0; i < fields.length; i++) { 
      jTextArea1.append(fields[i].getName() + " | " + fields[i].getType() + " | " + fields[i].get(clazz)); 

     } 
    } catch (Exception ex) { 
     ex.printStackTrace(); 
    } 
}           
} 

在按按鈕，它會成功寫入字段的名稱和類型。

當我想添加公共字段的值時，我很快就瞭解到，如果不聲明它們是靜態的（至少不是我所知），這是不可能的。

這就是儘管它是好的，爲外地來根據Java領域類文檔是一個實例字段： http://download.oracle.com/javase/1.4.2/docs/api/java/lang/reflect/Field.html

異常的堆棧跟蹤：

java.lang.IllegalArgumentException: Can not set java.lang.String field infosender.InfoSender.testInt to java.lang.Class 
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:146) 
at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:150) 
at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:37) 
at sun.reflect.UnsafeObjectFieldAccessorImpl.get(UnsafeObjectFieldAccessorImpl.java:18) 
at java.lang.reflect.Field.get(Field.java:358) 
at infosender.StatusGUI.jButton1ActionPerformed(StatusGUI.java:93) 
at infosender.StatusGUI.access$000(StatusGUI.java:22) 
at infosender.StatusGUI$1.actionPerformed(StatusGUI.java:54) 
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995) 
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318) 
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387) 
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242) 
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236) 
at java.awt.Component.processMouseEvent(Component.java:6289) 
at javax.swing.JComponent.processMouseEvent(JComponent.java:3267) 
at java.awt.Component.processEvent(Component.java:6054) 
at java.awt.Container.processEvent(Container.java:2041) 
at java.awt.Component.dispatchEventImpl(Component.java:4652) 
at java.awt.Container.dispatchEventImpl(Container.java:2099) 
at java.awt.Component.dispatchEvent(Component.java:4482) 
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577) 
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4238) 
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168) 
at java.awt.Container.dispatchEventImpl(Container.java:2085) 
at java.awt.Window.dispatchEventImpl(Window.java:2478) 
at java.awt.Component.dispatchEvent(Component.java:4482) 
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:644) 
at java.awt.EventQueue.access$000(EventQueue.java:85) 
at java.awt.EventQueue$1.run(EventQueue.java:603) 
at java.awt.EventQueue$1.run(EventQueue.java:601) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87) 
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98) 
at java.awt.EventQueue$2.run(EventQueue.java:617) 
at java.awt.EventQueue$2.run(EventQueue.java:615) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87) 
at java.awt.EventQueue.dispatchEvent(EventQueue.java:614) 
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) 
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) 
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) 
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122) 

欣賞任何幫助:) 邁克。

Answer 1

簡而言之，問題在於您使用的是Field.get()錯誤。你說：

fields[i].get(clazz) 

...其中clazz是類，你都試圖從字段值的對象。這就是爲什麼你只能看到靜態字段。你想要做的是這樣的：

fields[i].get(invokerObject) 

要獲得每個實例屬性的值，你需要傳遞要提取的值對象的實例，不的對象的實例類。

請注意，在致電fields[i].get()之前，您還可以致電fields[i].setAccessible(true)以獲得private和protected字段的值。

Answer 2

方法Field#get(Object)取實際對象從中提取值，而不是Class。所以它應該是

fields[i].get(invokerObject) 

所以invokerObject應設置爲，因此它可以被傳遞給你的jButton1ActionPerformed方法StatusGUI場。