Android中Binder詳細(xì)學(xué)習(xí)心得

public void setSystemProcess() {
  try {
    //注冊(cè)服務(wù)，第二個(gè)參數(shù)為this，這里假設(shè)SystemServer通過(guò)“socket”與SM交互
    ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true);
    ..........
  } catch (PackageManager.NameNotFoundException e) {
    ........
  }
}

int main(int argc, char **argv)
{
  struct binder_state *bs;
  //①應(yīng)該是打開(kāi)binder設(shè)備吧？
  bs = binder_open(128*1024);
  if (!bs) {
    ALOGE("failed to open binder driver\n");
    return -1;
  }
  //②成為manager
  if (binder_become_context_manager(bs)) {
    ALOGE("cannot become context manager (%s)\n", strerror(errno));
    return -1;
  }
  ......
  //③處理客戶端發(fā)過(guò)來(lái)的請(qǐng)求
  binder_loop(bs, svcmgr_handler);
  return 0;
}

struct binder_state*binder_open(unsigned mapsize)
{
  struct binder_state*bs;
  bs=malloc(sizeof(*bs));
  ......
  //打開(kāi)Binder設(shè)備
  bs->fd=open("/dev/binder"，O_RDWR);
  ......
  bs->mapsize=mapsize；
  //進(jìn)行內(nèi)存映射
  bs-＞mapped=mmap(NULL,mapsize,PROT_READ,MAP_PRIVATE,bs->
  fd,0);
}

int binder_become_context_manager(struct binder_state*bs)
{
  //實(shí)現(xiàn)太簡(jiǎn)單了!這個(gè)有個(gè)0，什么鬼？
  return ioctl(bs->fd,BINDER_SET_CONTEXT_MGR,0);
}

void binder_loop(struct binder_state *bs, binder_handler func)
{
  int res;
  struct binder_write_read bwr;
  uint32_t readbuf[32];
  bwr.write_size = 0;
  bwr.write_consumed = 0;
  bwr.write_buffer = 0;
  readbuf[0] = BC_ENTER_LOOPER;
  binder_write(bs, readbuf, sizeof(uint32_t));
  for (;;) {//果然是循環(huán)
    bwr.read_size = sizeof(readbuf);
    bwr.read_consumed = 0;
    bwr.read_buffer = (uintptr_t) readbuf;
    res = ioctl(bs->fd, BINDER_WRITE_READ, &bwr);
    if (res < 0) {
      ALOGE("binder_loop: ioctl failed (%s)\n", strerror(errno));
      break;
    }
    //接收到請(qǐng)求交給binder_parse，最終會(huì)調(diào)用func來(lái)處理這些請(qǐng)求
    res = binder_parse(bs, 0, (uintptr_t) readbuf, bwr.read_consumed, func);
    if (res == 0) {
      ALOGE("binder_loop: unexpected reply?!\n");
      break;
    }
    if (res < 0) {
      ALOGE("binder_loop: io error %d %s\n", res, strerror(errno));
      break;
    }
  }
}

public void setSystemProcess() {
  try {
    //注冊(cè)服務(wù)，第二個(gè)參數(shù)為this，這里假設(shè)SystemServer通過(guò)“socket”與SM交互
    ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true);
    ..........
  } catch (PackageManager.NameNotFoundException e) {
    ........
  }
}

public static void addService(String name, IBinder service) {
  try {
    getIServiceManager().addService(name, service, false);
  } catch (RemoteException e) {
    Log.e(TAG, "error in addService", e);
  }
}
private static IServiceManager getIServiceManager() {
  if (sServiceManager != null) {
    return sServiceManager;
  }
  // 是這里，沒(méi)錯(cuò)了
  sServiceManager = ServiceManagerNative.asInterface(BinderInternal.getContextObject());
  return sServiceManager;
}

//好吧，它還是個(gè)native函數(shù)
public static final native IBinder getContextObject();

static jobject android_os_BinderInternal_getContextObject(JNIEnv* env, jobject clazz)
{
  sp<IBinder> b = ProcessState::self()->getContextObject(NULL);
  return javaObjectForIBinder(env, b);
}

sp<IBinder> ProcessState::getContextObject(const sp<IBinder>& /*caller*/)
{
  return getStrongProxyForHandle(0);
}
/*這個(gè)函數(shù)是不是我們之前見(jiàn)過(guò)*/
sp<IBinder> ProcessState::getStrongProxyForHandle(int32_t handle)
{
  sp<IBinder> result;
  AutoMutex _l(mLock);
  handle_entry* e = lookupHandleLocked(handle);
  if (e != NULL) {
    IBinder* b = e->binder;
    if (b == NULL || !e->refs->attemptIncWeak(this)) {
      if (handle == 0) {//這里我們的handle為0
        Parcel data;
      //在handle對(duì)應(yīng)的BpBinder第一次創(chuàng)建時(shí)
      //會(huì)執(zhí)行一次虛擬的事務(wù)請(qǐng)求，以確保ServiceManager已經(jīng)注冊(cè)
        status_t status = IPCThreadState::self()->transact(
            0, IBinder::PING_TRANSACTION, data, NULL, 0);
        if (status == DEAD_OBJECT)
          return NULL;//如果ServiceManager沒(méi)有注冊(cè)，直接返回
      }
      //這里還是以handle參數(shù)創(chuàng)建了BpBinder
      b = new BpBinder(handle); 
      e->binder = b;
      if (b) e->refs = b->getWeakRefs();
      result = b;
    } else {
      
      result.force_set(b);
      e->refs->decWeak(this);
    }
  }
  return result;
}

static jobject android_os_BinderInternal_getContextObject(JNIEnv* env, jobject clazz)
{
  sp<IBinder> b = ProcessState::self()->getContextObject(NULL);
  //這里的b = new BpBinder(0);
  return javaObjectForIBinder(env, b);
}
/*這個(gè)函數(shù)我們上一篇是不是也見(jiàn)過(guò)*/
jobject javaObjectForIBinder(JNIEnv* env, const sp<IBinder>& val) {
  if (val == NULL) return NULL;
  //如果val是Binder對(duì)象，進(jìn)入下面分支，此時(shí)val是BpBinder
  if (val->checkSubclass(&gBinderOffsets)) {
    // One of our own!
    jobject object = static_cast<JavaBBinder*>(val.get())->object();
    LOGDEATH("objectForBinder %p: it's our own %p!\n", val.get(), object);
    return object;
  }
  .........
  //調(diào)用BpBinder的findObject函數(shù)
  //在Native層的BpBinder中有一個(gè)ObjectManager，它用來(lái)管理在Native BpBinder上創(chuàng)建的Java BinderProxy對(duì)象
  //findObject用于判斷gBinderProxyOffsets中，是否存儲(chǔ)了已經(jīng)被ObjectManager管理的Java BinderProxy對(duì)象
  jobject object = (jobject)val->findObject(&gBinderProxyOffsets);
  if (object != NULL) {
    jobject res = jniGetReferent(env, object);
    ............
    //如果該Java BinderProxy已經(jīng)被管理，則刪除這個(gè)舊的BinderProxy
    android_atomic_dec(&gNumProxyRefs);
    val->detachObject(&gBinderProxyOffsets);
    env->DeleteGlobalRef(object);
  }
  //創(chuàng)建一個(gè)新的BinderProxy對(duì)象
  object = env->NewObject(gBinderProxyOffsets.mClass, gBinderProxyOffsets.mConstructor);
  if (object != NULL) {
    env->SetLongField(object, gBinderProxyOffsets.mObject, (jlong)val.get());
    val->incStrong((void*)javaObjectForIBinder);
    jobject refObject = env->NewGlobalRef(
        env->GetObjectField(object, gBinderProxyOffsets.mSelf));
    //新創(chuàng)建的BinderProxy對(duì)象注冊(cè)到BpBinder的ObjectManager中，同時(shí)注冊(cè)一個(gè)回收函數(shù)proxy_cleanup
    //當(dāng)BinderProxy對(duì)象detach時(shí)，proxy_cleanup函數(shù)將被調(diào)用，以釋放一些資源
    val->attachObject(&gBinderProxyOffsets, refObject,
        jnienv_to_javavm(env), proxy_cleanup);
    // Also remember the death recipients registered on this proxy
    sp<DeathRecipientList> drl = new DeathRecipientList;
    drl->incStrong((void*)javaObjectForIBinder);
    //將死亡通知list和BinderProxy聯(lián)系起來(lái)
    env->SetLongField(object, gBinderProxyOffsets.mOrgue, reinterpret_cast<jlong>(drl.get()));
    // Note that a new object reference has been created.
    android_atomic_inc(&gNumProxyRefs);
    //垃圾回收相關(guān)；利用gNumRefsCreated記錄創(chuàng)建出的BinderProxy數(shù)量
    //當(dāng)創(chuàng)建出的BinderProxy數(shù)量大于200時(shí)，該函數(shù)將利用BinderInternal的ForceGc函數(shù)進(jìn)行一個(gè)垃圾回收
    incRefsCreated(env);
    return object;
  }
}

private static IServiceManager getIServiceManager() {
  if (sServiceManager != null) {
    return sServiceManager;
  }
  // 是這里，沒(méi)錯(cuò)了BinderInternal.getContextObject()是BinderProxy對(duì)象
  sServiceManager = ServiceManagerNative.asInterface(BinderInternal.getContextObject());
  return sServiceManager;
}

static public IServiceManager asInterface(IBinder obj)
{
  if (obj == null) {
    return null;
  }
  我們知道這里的obj指向的是BinderProxy對(duì)象
  IServiceManager in =
    (IServiceManager)obj.queryLocalInterface(descriptor);
  if (in != null) {
    return in;
  }
  return new ServiceManagerProxy(obj);
}

final class BinderProxy implements IBinder {
  public IInterface queryLocalInterface(String descriptor) {
    return null;
  }
}

class ServiceManagerProxy implements IServiceManager {
  public ServiceManagerProxy(IBinder remote) {
    //這里的mRemote指向了BinderProxy,與我們上一篇博客中講述的遙相呼應(yīng)
    mRemote = remote;
  }
}

interface IMyAidlInterface {
  int getTest();
}

public interface IMyAidlInterface extends android.os.IInterface {
  //抽象的Stub類，繼承自Binder并實(shí)現(xiàn)我們定義的IMyAidlInterface接口
  //繼承自Binder，重寫(xiě)onTransact方法，是不是感覺(jué)跟我們的XXXNative很像
  public static abstract class Stub extends android.os.Binder implements com.mafeibiao.testapplication.IMyAidlInterface {
    private static final java.lang.String DESCRIPTOR = "com.mafeibiao.testapplication.IMyAidlInterface";
    /**
     * Construct the stub at attach it to the interface.
     */
    public Stub() {
      this.attachInterface(this, DESCRIPTOR);
    }
    /**
     * Cast an IBinder object into an com.mafeibiao.testapplication.IMyAidlInterface interface,
     * generating a proxy if needed.
     */
    public static com.mafeibiao.testapplication.IMyAidlInterface asInterface(android.os.IBinder obj) {
      if ((obj == null)) {
        return null;
      }
      android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
      if (((iin != null) && (iin instanceof com.mafeibiao.testapplication.IMyAidlInterface))) {
        return ((com.mafeibiao.testapplication.IMyAidlInterface) iin);
      }
      return new com.mafeibiao.testapplication.IMyAidlInterface.Stub.Proxy(obj);
    }
    @Override
    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_getTest: {
          data.enforceInterface(DESCRIPTOR);
          int _result = this.getTest();
          reply.writeNoException();
          reply.writeInt(_result);
          return true;
        }
      }
      return super.onTransact(code, data, reply, flags);
    }
    /*這個(gè)Proxy不用說(shuō)肯定是代理了，其內(nèi)部還有個(gè)mRemote對(duì)象*/
    private static class Proxy implements com.mafeibiao.testapplication.IMyAidlInterface {
      private android.os.IBinder mRemote;

      Proxy(android.os.IBinder remote) {
        mRemote = remote;
      }
      @Override
      public android.os.IBinder asBinder() {
        return mRemote;
      }
      public java.lang.String getInterfaceDescriptor() {
        return DESCRIPTOR;
      }
      @Override
      public int getTest() 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_getTest, _data, _reply, 0);
          _reply.readException();
          _result = _reply.readInt();
        } finally {
          _reply.recycle();
          _data.recycle();
        }
        return _result;
      }
    }
    static final int TRANSACTION_getTest = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);
  }
  public int getTest() throws android.os.RemoteException;
}

package com.ryg.chapter_2.aidl;
/*這里顯示import*/
import com.ryg.chapter_2.aidl.Book;
interface IBookManager {
   //這里我們使用了自定義的Parcelable對(duì)象
   List<Book> getBookList();
   void addBook(in Book book);
}

package com.ryg.chapter_2.aidl;
parcelable Book;