Java 内部类

来源：互联网发布：大数据培训ujiuye 编辑：程序博客网时间：2024/06/11 16:36

参考http://android.blog.51cto.com/268543/384844

1、成员内部类

成员内部类，就是作为外部类的成员，可以直接使用外部类的所有成员和方法，即使是private的。同时外部类要访问内部类的所有成员变量/方法，则需要通过内部类的对象来获取。

要注意的是，成员内部类不能含有static的变量和方法。因为成员内部类需要先创建了外部类，才能创建它自己的，了解这一点，就可以明白更多事情，在此省略更多的细节了。在成员内部类要引用外部类对象时，使用outer.this来表示外部类对象；而需要创建内部类对象，可以使用outer.inner obj = outerobj.new inner();

public class Outer {     public static void main(String[] args) {         Outer outer = new Outer();         Outer.Inner inner = outer.new Inner();         inner.print("Outer.new");          inner = outer.getInner();         inner.print("Outer.get");     }      // 个人推荐使用getxxx()来获取成员内部类，尤其是该内部类的构造函数无参数时     public Inner getInner() {         return new Inner();     }      public class Inner {         public void print(String str) {             System.out.println(str);         }     } }

2、局部内部类

局部内部类，是指内部类定义在方法和作用域内。使用outer.this来表示外部类对象，注意name为final类型，局部内部类要使用形参name，必须加上final。Thinking in Java给了这么两个例子：

定义在方法内：

public class Outer {     public static void main(String[] args) {         Outer outer = new Outer();         Inner inner = outer.getInner("Inner", "gz");         System.out.println(inner.getName());     }      public Inner getInner(final String name, String city) { class InnerImp implements Inner {private String nameStr = name;public String getName() {return nameStr;}}return new InnerImp();     } } interface Inner {     String getName(); }

定义在作用域里：

public class Parcel5 {     private void internalTracking(boolean b) {         if (b) {             class TrackingSlip {                 private String id;                 TrackingSlip(String s) {                     id = s;                 }                 String getSlip() {                     return id;                 }             }             TrackingSlip ts = new TrackingSlip("slip");             String s = ts.getSlip();         }     }      public void track() {         internalTracking(true);     }      public static void main(String[] args) {         Parcel5 p = new Parcel5();         p.track();     } }

3、静态内部类

嵌套内部类，就是修饰为static的内部类。声明为static的内部类，不需要内部类对象和外部类对象之间的联系，就是说我们可以直接引用outer.inner，即不需要创建外部类，也不需要创建内部类。嵌套类和普通的内部类还有一个区别：普通内部类不能有static数据和static属性，也不能包含嵌套类，但嵌套类可以。而嵌套类不能声明为private，一般声明为public，方便调用。

静态内部类，就是修饰为static的内部类，不能引用外部类的成员和方法。不能声明为private，一般声明为public。

静态内部类，可以包含static的成员和方法，而成员内部类不能。

如果要生成静态内部类，outer.inner obj = new outerobj.inner();

/* * This file is auto-generated.  DO NOT MODIFY. * Original file: frameworks/base/core/java/android/os/IFregService.aidl */package android.os;public interface IFregService extends android.os.IInterface {/** Local-side IPC implementation stub class. */public static abstract class Stub extends android.os.Binder implementsandroid.os.IFregService {private static final java.lang.String DESCRIPTOR = "android.os.IFregService";/** Construct the stub at attach it to the interface. */public Stub() {this.attachInterface(this, DESCRIPTOR);}/** * Cast an IBinder object into an android.os.IFregService interface, * generating a proxy if needed. */public static android.os.IFregService asInterface(android.os.IBinder obj) {if ((obj == null)) {return null;}android.os.IInterface iin = (android.os.IInterface) obj.queryLocalInterface(DESCRIPTOR);if (((iin != null) && (iin instanceof android.os.IFregService))) {return ((android.os.IFregService) iin);}return new android.os.IFregService.Stub.Proxy(obj);}public android.os.IBinder asBinder() {return this;}@Overridepublic boolean onTransact(int code, android.os.Parcel data,android.os.Parcel reply, int flags)throws android.os.RemoteException {switch (code) {case INTERFACE_TRANSACTION: {reply.writeString(DESCRIPTOR);return true;}case TRANSACTION_setVal: {data.enforceInterface(DESCRIPTOR);int _arg0;_arg0 = data.readInt();this.setVal(_arg0);reply.writeNoException();return true;}case TRANSACTION_getVal: {data.enforceInterface(DESCRIPTOR);int _result = this.getVal();reply.writeNoException();reply.writeInt(_result);return true;}}return super.onTransact(code, data, reply, flags);}private static class Proxy implements android.os.IFregService {private android.os.IBinder mRemote;Proxy(android.os.IBinder remote) {mRemote = remote;}public android.os.IBinder asBinder() {return mRemote;}public java.lang.String getInterfaceDescriptor() {return DESCRIPTOR;}public void setVal(int val) throws android.os.RemoteException {android.os.Parcel _data = android.os.Parcel.obtain();android.os.Parcel _reply = android.os.Parcel.obtain();try {_data.writeInterfaceToken(DESCRIPTOR);_data.writeInt(val);mRemote.transact(Stub.TRANSACTION_setVal, _data, _reply, 0);_reply.readException();} finally {_reply.recycle();_data.recycle();}}public int getVal() throws android.os.RemoteException {android.os.Parcel _data = android.os.Parcel.obtain();android.os.Parcel _reply = android.os.Parcel.obtain();int _result;try {_data.writeInterfaceToken(DESCRIPTOR);mRemote.transact(Stub.TRANSACTION_getVal, _data, _reply, 0);_reply.readException();_result = _reply.readInt();} finally {_reply.recycle();_data.recycle();}return _result;}}static final int TRANSACTION_setVal = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);static final int TRANSACTION_getVal = (android.os.IBinder.FIRST_CALL_TRANSACTION + 1);}public void setVal(int val) throws android.os.RemoteException;public int getVal() throws android.os.RemoteException;}

4、匿名内部类

匿名内部类，使用outer.this来表示外部类对象。

((Button) findViewById(R.id.start)).setOnClickListener(new Button.OnClickListener() {     @Override     public void onClick(View v) {         new Thread() {              @Override             public void run() {                 // TODO Auto-generated method stub             }          }.start();     } });

对比局部内部类第一个例子，就能清楚的理解局部内部类的含义：

public class Outer {     public static void main(String[] args) {         Outer outer = new Outer();         Inner inner = outer.getInner("Inner", "gz");         System.out.println(inner.getName());     }      public Inner getInner(final String name, String city) {         return new Inner() {             private String nameStr = name;              public String getName() {                 return nameStr;             }         };    } } interface Inner {     String getName(); }

还有有参数的情况：

public class Outer {     public static void main(String[] args) {         Outer outer = new Outer();         Inner inner = outer.getInner("Inner", "gz");         System.out.println(inner.getName());     }      public Inner getInner(final String name, String city) {         return new Inner(name, city) {             private String nameStr = name;              public String getName() {                 return nameStr;             }         };     } }  abstract class Inner {     Inner(String name, String city) {         System.out.println(city);     }      abstract String getName(); }

还有一种aidl中，经常碰到的例子：

private IAcceleraterService.Stub mBinder = new IAcceleraterService.Stub() {@Overridepublic void stop() throws RemoteException {mAccServiceManager.stopAcc();}@Overridepublic void start() throws RemoteException {int flag = mAccServiceManager.startAcc(AcceleraterService.this);if (flag == 0) {Intent intent = new Intent(ACTION_START_SUCCESS);AcceleraterService.this.sendBroadcast(intent);} else {Intent intent = new Intent(ACTION_START_FAILURE);AcceleraterService.this.sendBroadcast(intent);}}@Overridepublic int resume() throws RemoteException {return mAccServiceManager.resumeAcc();}@Overridepublic int pause() throws RemoteException {return mAccServiceManager.pauseAcc();}@Overridepublic int isAvailable() throws RemoteException {return mAccServiceManager.isAccAvailable();}@Overridepublic int getHttpProxyPort() throws RemoteException {return mAccServiceManager.getAccHttpProxyPort();}@Overridepublic boolean isACCEnable() throws RemoteException {return AcceleraterServiceManager.isACCEnable();}@Overridepublic String getAccPort() throws RemoteException {return AcceleraterServiceManager.ACC_PORT;}@Overridepublic String getVersionName() throws RemoteException {return AcceleraterServiceManager.getAccVersionName();}@Overridepublic int getVersionCode() throws RemoteException {return AcceleraterServiceManager.getAccVersionCode();}@Overridepublic int getCurrentStatus() throws RemoteException {return mAccServiceManager.getCurrentStatus();}};

IAcceleraterService.Stub是一个抽象类。

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