寫給初學者，Android AIDL必看內容

更好的設計Android軟件應該熟悉掌握AIDL IPC機制，可以讓你編寫的組件類似Windows ActiveX COM一樣更好的復用，提供類似像SymBian那樣的服務器機制。服務可以很好的解決在後台運行無UI的窗口。我們創建一個aidl文件名為android123.aidl下面是示例代碼，修改於android SDK文檔。

一、創建AIDL文件

package cn.com.android123;

引入聲明 import cn.com.android123.IAtmService;

// 聲明一個接口，這裡演示的是銀行ATM程序
interface IBankAccountService {
    
    int getAccountBalance(); //返回整數，無參數
    void setOwnerNames(in List<String> names); //不返回，包含一個傳入List參數
    BankAccount createAccount(in String name, int startingDeposit, in IAtmService atmService); //返回一個自定義類型
    int getCustomerList(in String branch, out String[] customerList); //返回整形，輸入一個分支，輸出一個客戶列表
}

二、實現一個接口

顯示的提供一個導出接口，為客戶端提供綁定。

public class RemoteService extends Service {
    @Override
    public IBinder onBind(Intent intent) {
        if (IRemoteService.class.getName().equals(intent.getAction())) {
            return mBinder;
        }
        if (ISecondary.class.getName().equals(intent.getAction())) {
            return mSecondaryBinder;
        }
        return null;
    }

 //第一個接口

    private final IRemoteService.Stub mBinder = new IRemoteService.Stub() {
        public void registerCallback(IRemoteServiceCallback cb) {
            if (cb != null) mCallbacks.register(cb);
        }
        public void unregisterCallback(IRemoteServiceCallback cb) {
            if (cb != null) mCallbacks.unregister(cb);
        }
    };

//第二個接口

    private final ISecondary.Stub mSecondaryBinder = new ISecondary.Stub() {
        public int getPid() {
            return Process.myPid();
        }
        public void basicTypes(int anInt, long aLong, boolean aBoolean,
                float aFloat, double aDouble, String aString) {
        }
    };

}

三、客戶端交互

通過android.os提供的Parcelable類型來傳遞數據，通常我們使用Eclipse+ADT插件來完成，在Eclipse中在Package Explorer vIEw視圖上單擊鼠標右鍵，選擇Create Aidl preprocess file for Parcelable classes(創建aidl預編譯文件)，最終我們創建一個名為android123.aidl文件

import android.os.Parcel;
import android.os.Parcelable;

public final class Rect implements Parcelable {
    public int left;
    public int top;
    public int right;
    public int bottom;

    public static final Parcelable.Creator<Rect> CREATOR = new Parcelable.Creator<Rect>() {
        public Rect createFromParcel(Parcel in) {
            return new Rect(in);
        }

        public Rect[] newArray(int size) {
            return new Rect[size];
        }
    };

    public Rect() {
    }

    private Rect(Parcel in) {
        readFromParcel(in);
    }

    public void writeToParcel(Parcel out) { //當前數據寫入到Parcel中
        out.writeInt(left);
        out.writeInt(top);
        out.writeInt(right);
        out.writeInt(bottom);
    }

    public void readFromParcel(Parcel in) { //從Parcel中讀取數據
        left = in.readInt();
        top = in.readInt();
        right = in.readInt();
        bottom = in.readInt();
    }
}

  IPC調用方式

public class RemoteServiceBinding extends Activity {
    /** The primary interface we will be calling on the service. */
    IRemoteService mService = null;
    /** Another interface we use on the service. */
    ISecondary mSecondaryService = null;

    Button mKillButton;
    TextVIEw mCallbackText;

    private boolean mIsBound;

    /**
     * Standard initialization of this activity.  Set up the UI, then wait
     * for the user to poke it before doing anything.
     */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentVIEw(R.layout.remote_service_binding);

        // Watch for button clicks.
        Button button = (Button)findVIEwById(R.id.bind);
        button.setOnClickListener(mBindListener);
        button = (Button)findVIEwById(R.id.unbind);
        button.setOnClickListener(mUnbindListener);
        mKillButton = (Button)findVIEwById(R.id.kill);
        mKillButton.setOnClickListener(mKillListener);
        mKillButton.setEnabled(false);

        mCallbackText = (TextVIEw)findVIEwById(R.id.callback);
        mCallbackText.setText("Not attached.");
    }

    /**
     * Class for interacting with the main interface of the service.
     */
    private ServiceConnection mConnection = new ServiceConnection() {
        public void onServiceConnected(ComponentName className,
                IBinder service) {
            // This is called when the connection with the service has been
            // established, giving us the service object we can use to
            // interact with the service.  We are communicating with our
            // service through an IDL interface, so get a clIEnt-side
            // representation of that from the raw service object.
            mService = IRemoteService.Stub.asInterface(service);
            mKillButton.setEnabled(true);
            mCallbackText.setText("Attached.");

            // We want to monitor the service for as long as we are
            // connected to it.
            try {
                mService.registerCallback(mCallback);
            } catch (RemoteException e) {
                // In this case the service has crashed before we could even
                // do anything with it; we can count on soon being
                // disconnected (and then reconnected if it can be restarted)
                // so there is no need to do anything here.
            }

            // As part of the sample, tell the user what happened.
            Toast.makeText(RemoteServiceBinding.this, R.string.remote_service_connected,
                    Toast.LENGTH_SHORT).show();
        }

        public void onServiceDisconnected(ComponentName className) {
            // This is called when the connection with the service has been
            // unexpectedly disconnected -- that is, its process crashed.
            mService = null;
            mKillButton.setEnabled(false);
            mCallbackText.setText("Disconnected.");

            // As part of the sample, tell the user what happened.
            Toast.makeText(RemoteServiceBinding.this, R.string.remote_service_disconnected,
                    Toast.LENGTH_SHORT).show();
        }
    };

    /**
     * Class for interacting with the secondary interface of the service.
     */
    private ServiceConnection mSecondaryConnection = new ServiceConnection() {
        public void onServiceConnected(ComponentName className,
                IBinder service) {
            // Connecting to a secondary interface is the same as any
            // other interface.
            mSecondaryService = ISecondary.Stub.asInterface(service);
            mKillButton.setEnabled(true);
        }

        public void onServiceDisconnected(ComponentName className) {
            mSecondaryService = null;
            mKillButton.setEnabled(false);
        }
    };

    private OnClickListener mBindListener = new OnClickListener() {
        public void onClick(VIEw v) {
            // Establish a couple connections with the service, binding
            // by interface names.  This allows other applications to be
            // installed that replace the remote service by implementing
            // the same interface.
            bindService(new Intent(IRemoteService.class.getName()),
                    mConnection, Context.BIND_AUTO_CREATE);
            bindService(new Intent(ISecondary.class.getName()),
                    mSecondaryConnection, Context.BIND_AUTO_CREATE);
            mIsBound = true;
            mCallbackText.setText("Binding.");
        }
    };

    private OnClickListener mUnbindListener = new OnClickListener() {
        public void onClick(VIEw v) {
            if (mIsBound) {
                // If we have received the service, and hence registered with
                // it, then now is the time to unregister.
                if (mService != null) {
                    try {
                        mService.unregisterCallback(mCallback);
                    } catch (RemoteException e) {
                        // There is nothing special we need to do if the service
                        // has crashed.
                    }
                }

                // Detach our existing connection.
                unbindService(mConnection);
                unbindService(mSecondaryConnection);
                mKillButton.setEnabled(false);
                mIsBound = false;
                mCallbackText.setText("Unbinding.");
            }
        }
    };

    private OnClickListener mKillListener = new OnClickListener() {
        public void onClick(VIEw v) {
            // To kill the process hosting our service, we need to know its
            // PID.  ConvenIEntly our service has a call that will return
            // to us that information.
            if (mSecondaryService != null) {
                try {
                    int pid = mSecondaryService.getPid();
                    // Note that, though this API allows us to request to
                    // kill any process based on its PID, the kernel will
                    // still impose standard restrictions on which PIDs you
                    // are actually able to kill.  Typically this means only
                    // the process running your application and any additional
                    // processes created by that app as shown here; packages
                    // sharing a common UID will also be able to kill each
                    // other's processes.
                    Process.killProcess(pid);
                    mCallbackText.setText("Killed service process.");
                } catch (RemoteException ex) {
                    // Recover gracefully from the process hosting the
                    // server dying.
                    // Just for purposes of the sample, put up a notification.
                    Toast.makeText(RemoteServiceBinding.this,
                            R.string.remote_call_failed,
                            Toast.LENGTH_SHORT).show();
                }
            }
        }
    };

    // ----------------------------------------------------------------------
    // Code showing how to deal with callbacks.
    // ----------------------------------------------------------------------

    /**
     * This implementation is used to receive callbacks from the remote
     * service.
     */
    private IRemoteServiceCallback mCallback = new IRemoteServiceCallback.Stub() {
        /**
         * This is called by the remote service regularly to tell us about
         * new values.  Note that IPC calls are dispatched through a thread
         * pool running in each process, so the code executing here will
         * NOT be running in our main thread like most other things -- so,
         * to update the UI, we need to use a Handler to hop over there.
         */
        public void valueChanged(int value) {
            mHandler.sendMessage(mHandler.obtainMessage(BUMP_MSG, value, 0));
        }
    };

    private static final int BUMP_MSG = 1;

    private Handler mHandler = new Handler() {
        @Override public void handleMessage(Message msg) {
            switch (msg.what) {
                case BUMP_MSG:
                    mCallbackText.setText("Received from service: " + msg.arg1);
                    break;
                default:
                    super.handleMessage(msg);
            }
        }

    };
}