更好的设计Android软件应该熟悉掌握AIDL IPC机制，可以让你编写的组件类似Windows ActiveX COM一样更好的复用，提供类似像Symbian那样的服务器机制。服务可以很好的解决在后台运行无UI的窗口。我们创建一个aidl文件名为 android123.aidl下面是示例代码，修改于Android SDK文档。
[代码] 一、创建AIDL文件
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ackage cn.com.android123;
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引入声明
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import cn.com.android123.IAtmService;
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// 声明一个接口，这里演示的是银行ATM程序
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interface IBankAccountService {
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int getAccountBalance(); //返回整数，无参数
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void setOwnerNames(in List<String> names); //不返回，包含一个传入List参数
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BankAccount createAccount(in String name, int startingDeposit, in IAtmService atmService); //返回一个自定义类型
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int getCustomerList(in String branch, out String[] customerList); //返回整形，输入一个分支，输出一个客户列表
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}
[代码] 二、实现一个接口
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//显示的提供一个导出接口，为客户端提供绑定。
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public class RemoteService extends Service {
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@Override
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public IBinder onBind(Intent intent) {
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if (IRemoteService.class.getName().equals(intent.getAction())) {
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return mBinder;
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}
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if (ISecondary.class.getName().equals(intent.getAction())) {
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return mSecondaryBinder;
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}
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return null;
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}
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//第一个接口
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private final IRemoteService.Stub mBinder = new IRemoteService.Stub() {
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public void registerCallback(IRemoteServiceCallback cb) {
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if (cb != null) mCallbacks.register(cb);
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}
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public void unregisterCallback(IRemoteServiceCallback cb) {
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if (cb != null) mCallbacks.unregister(cb);
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}
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};
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//第二个接口
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private final ISecondary.Stub mSecondaryBinder = new ISecondary.Stub() {
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public int getPid() {
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return Process.myPid();
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}
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public void basicTypes(int anInt, long aLong, boolean aBoolean,
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float aFloat, double aDouble, String aString) {
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}
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};
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}
[代码] 三、客户端交互
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/**
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通过Android.os提供的Parcelable类型来传递数据，通常我们使用Eclipse+ADT插件来完成，在Eclipse中在Package Explorer view视图上单击鼠标右键，选择Create Aidl preprocess file for Parcelable classes(创建aidl预编译文件)，最终我们创建一个名为android123.aidl文件
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*/
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import android.os.Parcel;
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import android.os.Parcelable;
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public final class Rect implements Parcelable {
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public int left;
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public int top;
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public int right;
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public int bottom;
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public static final Parcelable.Creator<Rect> CREATOR = new Parcelable.Creator<Rect>() {
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public Rect createFromParcel(Parcel in) {
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return new Rect(in);
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}
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public Rect[] newArray(int size) {
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return new Rect[size];
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}
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};
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public Rect() {
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}
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private Rect(Parcel in) {
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readFromParcel(in);
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}
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public void writeToParcel(Parcel out) { //当前数据写入到Parcel中
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out.writeInt(left);
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out.writeInt(top);
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out.writeInt(right);
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out.writeInt(bottom);
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}
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public void readFromParcel(Parcel in) { //从Parcel中读取数据
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left = in.readInt();
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top = in.readInt();
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right = in.readInt();
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bottom = in.readInt();
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}
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}
[代码] IPC调用方式
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public class RemoteServiceBinding extends Activity {
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/** The primary interface we will be calling on the service. */
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IRemoteService mService = null;
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/** Another interface we use on the service. */
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ISecondary mSecondaryService = null;
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Button mKillButton;
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TextView mCallbackText;
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private boolean mIsBound;
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/**
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* Standard initialization of this activity.Set up the UI, then wait
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* for the user to poke it before doing anything.
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*/
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@Override
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protected void onCreate(Bundle savedInstanceState) {
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super.onCreate(savedInstanceState);
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setContentView(R.layout.remote_service_binding);
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// Watch for button clicks.
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Button button = (Button)findViewById(R.id.bind);
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button.setOnClickListener(mBindListener);
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button = (Button)findViewById(R.id.unbind);
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button.setOnClickListener(mUnbindListener);
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mKillButton = (Button)findViewById(R.id.kill);
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mKillButton.setOnClickListener(mKillListener);
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mKillButton.setEnabled(false);
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mCallbackText = (TextView)findViewById(R.id.callback);
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mCallbackText.setText("Not attached.");
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}
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/**
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* Class for interacting with the main interface of the service.
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*/
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private ServiceConnection mConnection = new ServiceConnection() {
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public void onServiceConnected(ComponentName className,
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IBinder service) {
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// This is called when the connection with the service has been
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// established, giving us the service object we can use to
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// interact with the service.We are communicating with our
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// service through an IDL interface, so get a client-side
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// representation of that from the raw service object.
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mService = IRemoteService.Stub.asInterface(service);
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mKillButton.setEnabled(true);
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mCallbackText.setText("Attached.");
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// We want to monitor the service for as long as we are
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// connected to it.
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try {
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mService.registerCallback(mCallback);
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} catch (RemoteException e) {
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// In this case the service has crashed before we could even
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// do anything with it; we can count on soon being
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// disconnected (and then reconnected if it can be restarted)
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// so there is no need to do anything here.
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}
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// As part of the sample, tell the user what happened.
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Toast.makeText(RemoteServiceBinding.this, R.string.remote_service_connected,
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Toast.LENGTH_SHORT).show();
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}
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public void onServiceDisconnected(ComponentName className) {
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// This is called when the connection with the service has been
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// unexpectedly disconnected -- that is, its process crashed.
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mService = null;
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mKillButton.setEnabled(false);
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mCallbackText.setText("Disconnected.");
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// As part of the sample, tell the user what happened.
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Toast.makeText(RemoteServiceBinding.this, R.string.remote_service_disconnected,
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Toast.LENGTH_SHORT).show();
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}
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};
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/**
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* Class for interacting with the secondary interface of the service.
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*/
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private ServiceConnection mSecondaryConnection = new ServiceConnection() {
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public void onServiceConnected(ComponentName className,
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IBinder service) {
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// Connecting to a secondary interface is the same as any
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// other interface.
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mSecondaryService = ISecondary.Stub.asInterface(service);
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mKillButton.setEnabled(true);
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}
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public void onServiceDisconnected(ComponentName className) {
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mSecondaryService = null;
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mKillButton.setEnabled(false);
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}
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};
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private OnClickListener mBindListener = new OnClickListener() {
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public void onClick(View v) {
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// Establish a couple connections with the service, binding
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// by interface names.This allows other applications to be
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// installed that replace the remote service by implementing
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// the same interface.
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bindService(new Intent(IRemoteService.class.getName()),
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mConnection, Context.BIND_AUTO_CREATE);
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bindService(new Intent(ISecondary.class.getName()),
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mSecondaryConnection, Context.BIND_AUTO_CREATE);
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mIsBound = true;
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mCallbackText.setText("Binding.");
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}
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};
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private OnClickListener mUnbindListener = new OnClickListener() {
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public void onClick(View v) {
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if (mIsBound) {
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// If we have received the service, and hence registered with
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// it, then now is the time to unregister.
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if (mService != null) {
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try {
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mService.unregisterCallback(mCallback);
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} catch (RemoteException e) {
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// There is nothing special we need to do if the service
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// has crashed.
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}
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}
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// Detach our existing connection.
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unbindService(mConnection);
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unbindService(mSecondaryConnection);
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mKillButton.setEnabled(false);
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mIsBound = false;
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mCallbackText.setText("Unbinding.");
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}
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}
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};
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private OnClickListener mKillListener = new OnClickListener() {
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public void onClick(View v) {
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// To kill the process hosting our service, we need to know its
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// PID.Conveniently our service has a call that will return
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// to us that information.
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if (mSecondaryService != null) {
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try {
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int pid = mSecondaryService.getPid();
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// Note that, though this API allows us to request to
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// kill any process based on its PID, the kernel will
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// still impose standard restrictions on which PIDs you
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// are actually able to kill.Typically this means only
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// the process running your application and any additional
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// processes created by that app as shown here; packages
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// sharing a common UID will also be able to kill each
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// other's processes.
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Process.killProcess(pid);
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mCallbackText.setText("Killed service process.");
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} catch (RemoteException ex) {
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// Recover gracefully from the process hosting the
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// server dying.
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// Just for purposes of the sample, put up a notification.
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Toast.makeText(RemoteServiceBinding.this,
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R.string.remote_call_failed,
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Toast.LENGTH_SHORT).show();
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}
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}
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}
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};
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// ----------------------------------------------------------------------
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// Code showing how to deal with callbacks.
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// ----------------------------------------------------------------------
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/**
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* This implementation is used to receive callbacks from the remote
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* service.
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*/
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private IRemoteServiceCallback mCallback = new IRemoteServiceCallback.Stub() {
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/**
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* This is called by the remote service regularly to tell us about
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* new values.Note that IPC calls are dispatched through a thread
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* pool running in each process, so the code executing here will
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* NOT be running in our main thread like most other things -- so,
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* to update the UI, we need to use a Handler to hop over there.
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*/
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public void valueChanged(int value) {
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mHandler.sendMessage(mHandler.obtainMessage(BUMP_MSG, value, 0));
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}
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};
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private static final int BUMP_MSG = 1;
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private Handler mHandler = new Handler() {
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@Override public void handleMessage(Message msg) {
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switch (msg.what) {
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case BUMP_MSG:
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mCallbackText.setText("Received from service: " + msg.arg1);
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break;
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default:
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super.handleMessage(msg);
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}
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}
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};
