Java 内部类
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public,一般声明为private。
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 implements android.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; } @Override public 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(); }
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() { @Override public void stop() throws RemoteException { mAccServiceManager.stopAcc(); } @Override public 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); } } @Override public int resume() throws RemoteException { return mAccServiceManager.resumeAcc(); } @Override public int pause() throws RemoteException { return mAccServiceManager.pauseAcc(); } @Override public int isAvailable() throws RemoteException { return mAccServiceManager.isAccAvailable(); } @Override public int getHttpProxyPort() throws RemoteException { return mAccServiceManager.getAccHttpProxyPort(); } @Override public boolean isACCEnable() throws RemoteException { return AcceleraterServiceManager.isACCEnable(); } @Override public String getAccPort() throws RemoteException { return AcceleraterServiceManager.ACC_PORT; } @Override public String getVersionName() throws RemoteException { return AcceleraterServiceManager.getAccVersionName(); } @Override public int getVersionCode() throws RemoteException { return AcceleraterServiceManager.getAccVersionCode(); } @Override public int getCurrentStatus() throws RemoteException { return mAccServiceManager.getCurrentStatus(); } };IAcceleraterService.Stub是一个抽象类。
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