Android IPC/Binder Framework 实战（上）

Android IPC 框架 实战

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笔记
https://thenewcircle.com/s/post/1340/Deep_Dive_Into_Binder_Presentation.htm

知识点

• Binder Overview
• IPC
• Advantages of Binder
• Binder vs Intent/ContentProvider/Messenger-based IPC
• Binder Terminology
• Binder Communication and Discovery
• AIDL
• Binder Object Reference Mapping
• Binder by Example
• Async Binder
• Memory Sharing
• Binder Limitations
• Security

什么是 Binder ？

An IPC/component system for developing object-oriented OS services.
不支持 RPC

• 什么是 IPC？
  
  • 一种在进程间相互交换数据和信号的框架；
  • 用于消息传递，同步，共享内存和远程调用
• IPC的选择
  
  • 文件、信号/信号量、套接字、管道、消息队列；
  • Intents、ContentProviders、Messenger、Binder；
• Why Binder?
  
  • Its built-in reference-counting of "object" references plus death-notification mechanism make it suitable for "hostile" environments (where lowmemorykiller roams)
  • When a binder service is no longer referenced by any clients, its owner is automatically notified that it can dispose of it
• 其它：
  
  • 大多数 app 组件的生命周期回调方法（ onResume(), onDestory() 等）由 ActivityManagerService 使用 Binder 进行回调

IPC 与 Intents 和 ContentProviders

• Android 系统支持一种便捷的 IPC 实现 ：Intents 和 ContentProviders
• ContentResolvers 通过 CRUD API 与 ContentProviders 进行异步通信；所有的通信默认在主线程 Looper 中进行；

Messenger IPC

• Handler 以 Messenger 为代表通过 Intent 与远程进程进行通信。
• Android's Messenger represents a reference to a Handler that can be sent to a remote process via an Intent
  

代码示例

public class DownloadClientActivity extends Activity {
    private static final int CALLBACK_MSG = 0;
    …
    @Override
    public void onClick(View view) {
        Intent intent = new Intent("com.marakana.android.download.service.SERVICE");
        ArrayList<Uri> uris = …
        intent.putExtra("uris", uris);
        Messenger messenger = new Messenger(new ClientHandler(this));
        intent.putExtra("callback-messenger", messenger);
        super.startService(intent);
    }
    private static class ClientHandler extends Handler {
        private final WeakReference<DownloadClientActivity> clientRef;
        public ClientHandler(DownloadClientActivity client) {
            this.clientRef = new WeakReference<DownloadClientActivity>(client);
        }
        @Override
        public void handleMessage(Message msg) {  
            Bundle data = msg.getData();
            DownloadClientActivity client = clientRef.get();
            if (client != null && msg.what == CALLBACK_MSG && data != null) {
                Uri completedUri = data.getString("completed-uri");
                // client now knows that completedUri is done
                …
            }
         }
     }
}
public class MessengerDemoService extends IntentService {
    private static final int CALLBACK_MSG = 0;
    …
    @Override
    protected void onHandleIntent(Intent intent) {
        ArrayList<Uri> uris = intent.getParcelableArrayListExtra("uris");
        Messenger messenger = intent.getParcelableExtra("callback-messenger");
        for (Uri uri : uris) {
           // download the uri
           …
           if (messenger != null) {
               Message message = Message.obtain();
               message.what = CALLBACK_MSG;
               Bundle data = new Bundle(1);
               data.putParcelable("completed-uri", uri);
               message.setData(data);       
               try {
                   messenger.send(message);
               } catch (RemoteException e) {
                   …   
               } finally {
                  message.recycle(); 
               }
          }
       }
    }
}

Binder Terminology

• 每个进程仅最大支持 15 个 Binder 线程
• 避免阻塞 Binder 线程，长时间操作建议自建线程处理
• Binder 限制每个进程最大只有 1 Mb 的 transactional buffer （TransactionTooLargeException）
  

AIDL

Android Interface Definition Language is a Android-specific language for defining Binder-based service interfaces

• AIDL supports the following types:
  
  • null
  • boolean, boolean[], byte, byte[], char[], int, int[], long, long[], float, float[], double, double[]
  • java.lang.CharSequence, java.lang.String (sent as UTF-16)
  • java.io.FileDescriptor
  • java.io.Serializable - not efficient
  • java.util.Map - of supported types (always reconstructed as java.util.HashMap)
  • android.os.Bundle
  • java.util.List
  • java.lang.Object[]
  • android.util.SparseArray, android.util.SparseBooleanArray
  • android.os.IBinder, android.os.IInterface

src/com/example/app/IFooService.aidl

package com.example.app;
import com.example.app.Bar;
interface IFooService {
    void save(inout Bar bar);
    Bar getById(int id);
    void delete(in Bar bar);
    List<Bar> getAll();
} 

Binder Object Reference

• A binder object reference is one of the following
  
  • An actual virtual memory address to a binder object in the same process
  • An abstract 32-bit handle to a binder object in another process

命令

$ adb shell service list

实战

https://github.com/mSoloYu/StockQuoteDemo.git

• StockQuoteAidl : Define AIDL Interface and Custom Types ( Android library project )
  

// IStockQuoteService.aidl
package com.stockquote.example;
// Declare any non-default types here with import statements
import com.stockquote.example.StockQuoteRequest;
import com.stockquote.example.StockQuoteResponse;
interface IStockQuoteService {
    StockQuoteResponse retrieveStockQuote(in StockQuoteRequest request);
}
// StockQuoteResponse.aidl
package com.stockquote.example;pp
Parcelable StockQuoteResponse;
// StockQuoteResponse.java
public class StockQuoteResponse implements Parcelable {
    private final StockQuote mResult;
    public StockQuoteResponse(StockQuote result) {
        mResult = result;
    }
    public StockQuote getResult() {
        return mResult;
    }
    public int describeContents() {
        return 0;
    }
    public void writeToParcel(Parcel parcel, int flags) {
        parcel.writeSerializable(mResult);
    }
    public static final Parcelable.Creator<StockQuoteResponse> CREATOR 
            = new Parcelable.Creator<StockQuoteResponse>() {
        public StockQuoteResponse createFromParcel(Parcel in) {
            return new StockQuoteResponse((StockQuote)in.readSerializable());
        }
        public StockQuoteResponse[] newArray(int size) {
            return new StockQuoteResponse[size];
        }
    };
}

• StockQuoteServer : Implement AIDL Interface and Expose It To Our Clients (app project)
  

<service android:name="com.stockquote.server.StockQuoteService">
         <intent-filter>
                <action android:name="com.stockquote.example.IStockQuoteService" />
         </intent-filter>
</service>

// StockQuoteServiceImpl.java
public class StockQuoteServiceImpl extends IStockQuoteService.Stub {
    private static final String TAG = "StockQuoteServiceImpl";
    @Override
    public StockQuoteResponse retrieveStockQuote(StockQuoteRequest request)
            throws RemoteException {
        String[] stockIdArray = null;
        if (request.getType() == StockQuoteRequest.Type.STOCKQUOTE_MULTIPLE) {
            stockIdArray = request.getStockIdArray();
        } else {
            return null;
        }
        StockQuote stockQuote = StockNetResourceManager.getInstance()
                .setUpStockQuotes(stockIdArray);
        return new StockQuoteResponse(stockQuote);
    }
}
// StockQuoteService
public class StockQuoteService extends Service {
    private static final String TAG = "StockQuoteService";
    private StockQuoteServiceImpl mService;
    @Override
    public void onCreate() {
        super.onCreate();
        mService = new StockQuoteServiceImpl();
    }
    @Override
    public IBinder onBind(Intent intent) {
        return mService;
    }
    @Override
    public boolean onUnbind(Intent intent) {
        return super.onUnbind(intent);
    }
    @Override
    public void onDestroy() {
        mService = null;
        super.onDestroy();
    }
}
// StockNetResourceManager.java
public class StockNetResourceManager {
    private static final String URL_STOCK_REC = "http://hq.sinajs.cn/list=";
    private static final StockNetResourceManager INSTANCE = new StockNetResourceManager();
    private final OkHttpClient client = new OkHttpClient();
    private StockNetResourceManager() {
    }
    public static StockNetResourceManager getInstance() {
        return INSTANCE;
    }
    public StockQuote setUpStockQuotes(String[] stockIds) {
        StringBuilder stockRecUrl = new StringBuilder(URL_STOCK_REC);
        for (String stockId : stockIds) {
            makeRealStockId(stockId, stockRecUrl);
            stockRecUrl.append(",");
        }
        stockRecUrl.deleteCharAt(stockRecUrl.length() - 1);
        Request request = new Request.Builder().url(stockRecUrl.toString()).build();
        try {
            return cookStockQuote(client.newCall(request).execute().body().string());
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
    public StockQuote cookStockQuote(String rawRecs) {
        // var hq_str_sz002024="苏宁云商,11.26,11.22,11.33,11.45,11.17,11.33,11.34,131241390,1484755809.02,
        // 153559,11.33,358350,11.32,396400,11.31,654870,11.30,151700,11.29,420400,11.34,315415,11.35,170927,11.36,202600,11.37,111001,11.38,
        // 2015-03-13,15:05:53,00";
        // name,open,lastClose,current,highest,lowest,close,**,vol(手),money(元),
        // after split, the related index will be :
        String[] stockRecItemArray = rawRecs.split(",");
        String name = stockRecItemArray[0].split("\"")[1];
        // hanlde suspend day
        if (stockRecItemArray[1].startsWith("0.000")) {
            return new StockQuote(StockQuote.EVEN_COLOR, name, stockRecItemArray[3],
                    stockRecItemArray[3], stockRecItemArray[3], "+0.00", "+0.00%");
        }
        String lastPriceStr = stockRecItemArray[2];
        String curPriceStr = stockRecItemArray[3];
        int lastPrice = Integer.parseInt(lastPriceStr.replace(".", ""));
        int curPrice = Integer.parseInt(curPriceStr.replace(".", ""));
        int priceColor = StockQuote.EVEN_COLOR;
        if (curPrice > lastPrice) {
            priceColor = StockQuote.RISE_COLOR;
        } else if (curPrice < lastPrice) {
            priceColor = StockQuote.DOWN_COLOR;
        }
        float dividerForGap = 100.00f;
        float divider = 100.00f;
        if (name.startsWith("上证指数") || name.startsWith("深证成指")) {
            dividerForGap = 1000.00f;
            stockRecItemArray[3] = stockRecItemArray[3].substring(0, stockRecItemArray[3].length() - 1);
            stockRecItemArray[4] = stockRecItemArray[4].substring(0, stockRecItemArray[4].length() - 1);
            stockRecItemArray[5] = stockRecItemArray[5].substring(0, stockRecItemArray[5].length() - 1);
        }
        String priceGap = String.format("%+.2f", (curPrice - lastPrice)/dividerForGap);
        String percentage = String.format("%+.2f%%", (curPrice - lastPrice) * divider/lastPrice);
        return new StockQuote(priceColor, name, stockRecItemArray[3],
                stockRecItemArray[4], stockRecItemArray[5], priceGap, percentage);
    }
    private void makeRealStockId(String stockId, StringBuilder realStockIdBuilder) {
        if (stockId.startsWith("sh") || stockId.startsWith("sz")) {
            realStockIdBuilder.append(stockId);
            return ;
        }
        if (stockId.startsWith("600") || stockId.startsWith("601")) {
            realStockIdBuilder.append("sh").append(stockId);
        } else {
            realStockIdBuilder.append("sz").append(stockId);
        }
    }
}

• StockQuoteClient : Using AIDL-defined Binder-based Services (app project)
  

public class MainActivity extends Activity 
        implements ServiceConnection {
    private static final String TAG = "MainActivity";
    private TextView mNameTv;
    private TextView mQuoteTv;
    private IStockQuoteService mService;
    @Override
    protected void onCreate(Bundle savedBundle) {
        super.onCreate(savedBundle);
        setContentView(R.layout.main);
        mNameTv = (TextView) findViewById(R.id.name);
        mQuoteTv = (TextView) findViewById(R.id.quote);
    }
    @Override
    protected void onResume() {
        super.onResume();
        if (!super.bindService(new Intent(IStockQuoteService.class.getName()),
                this, BIND_AUTO_CREATE)) {
        }
    }
    @Override
    protected void onPause() {
        super.onPause();
        super.unbindService(this);
    }
    public void onServiceConnected(ComponentName name, IBinder service) {
        mService = IStockQuoteService.Stub.asInterface(service);
        setText();
    }
    public void onServiceDisconnected(ComponentName name) {
        mService = null;
    }
    private void setText() {
        final StockQuoteRequest request = new StockQuoteRequest(null, 
                new String[]{"002024"}, StockQuoteRequest.Type.STOCKQUOTE_MULTIPLE);
        final ProgressDialog dialog = ProgressDialog.show(this, "",
                "正在获取...", true);
        new AsyncTask<Void, Void, StockQuote>() {
            @Override
            protected StockQuote doInBackground(Void... params) {
                try {
                    StockQuoteResponse response = mService.retrieveStockQuote(request);
                    dialog.dismiss();
                    return response.getResult();
                } catch (RemoteException e) {
                    Log.wtf(TAG, "Failed to communicate with the service", e);
                    dialog.dismiss();
                    return null;
                }
            }
            @Override
            protected void onPostExecute(StockQuote result) {
                dialog.dismiss();
                if (result == null) {
                    Toast.makeText(MainActivity.this, "获取失败",
                            Toast.LENGTH_LONG).show();
                } else {
                    mNameTv.setText(result.getStockName());
                    mQuoteTv.setText(result.getStockPrice());
                }
            }
        }.execute();
    }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/name"
        android:gravity="center_horizontal|center_vertical"
        android:layout_weight="1"
        android:layout_width="match_parent"
        android:layout_height="0dp" />
    <TextView
        android:id="@+id/quote"
        android:gravity="center_horizontal|center_vertical"
        android:layout_weight="1"
        android:layout_width="match_parent"
        android:layout_height="0dp" />
</LinearLayout>