揭阳网站建设策划方案,土建网招聘信息,住房和城乡建设部网站造价,wordpress 菜单 数据库前言 众所周知#xff0c;对于binder通信来说#xff0c;native层通信的基础架构是BpBinder/BBinder#xff0c;Java层的基础通信架构是BinderProxy/Binder#xff0c;这两者是如何统一起来的呢#xff1f;
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在binder的跨进程传递数据实现中#xff0c;数据是包裹在…前言 众所周知对于binder通信来说native层通信的基础架构是BpBinder/BBinderJava层的基础通信架构是BinderProxy/Binder这两者是如何统一起来的呢
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在binder的跨进程传递数据实现中数据是包裹在Parcel中的。具体的传递方式体现在Parcel类的两个方法writeStrongBinder()和readStrongBinder()中前者的功能是写入Binder对象后者的功能是读取Binder对象。同样Parcel在java层和native层各有一套。不过查看代码可知java层的Parcel只是native层的封装两者通过jni建立关联。 public final void writeStrongBinder(IBinder val){nativeWriteStrongBinder(mNativePtr, val);}public final IBinder readStrongBinder(){return nativeReadStrongBinder(mNativePtr);}private static native String nativeReadStrongBinder(long nativePtr);private static native void nativeWriteStrongBinder(long natievPtr, IBinder);
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jni层代码如下 static void android_os_Parcel_writeStrongBinder(JNIEnv* env, jclass clazz, jlong nativePtr, jobject object){Parcel* parcel reinterpret_castParcel*(nativePtr);if (parcel ! NULL){const status_t err parcel-writeStrongBinder(ibinderForJavaObject(env, object));if (err ! NO_ERROR){signalExceptionForError(env, clazz, err);}}}static jobject android_os_Parcel_readStrongBinder(JNIEnv* env, jclass clazz, jlong nativePtr){Parcel* parcel reinterpret_castParcel*(nativePtr);if (parcel ! NULL){return javaObjectForIBinder(env, parcel-readStrongBinder());}return NULL;}
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重点来了在jni层代码中发现了两个名字起的有点意思的函数ibinderForJavaObject()和javaObjectForIBinder()正是这两个函数将java层和native层统一了代码如下 spIBinder ibinderForJavaObject(JNIEnv* env, jobject obj){if (obj NULL) return NULL;//Instance of Binder?if (env-IsInstanceOf(obj, gBinderOffsets.mClass)){JavaBBinderHolder* jbh (JavaBBinderHolder*)env-GetLongField(obj, gBinderOffsets.mObject);return jbh-get(env, obj);}//Instance of BinderProxy?if (env-IsInstanceOf(obj, gBinderProxyOffsets.mClass)){return getBPNativeData(env, obj)-mObject;}return NULL;}jobject javaObjectForIBinder(JNIEnv* env, const spIBinder val){if (val NULL) return NULL;if (val-checkSubclass(gBinderOffsets)){//Its a JavaBBinder created by ibinderForJavaObjectjobject object static_castJavaBBinder*(val.get())-object();return object;}BinderProxyNativeData* nativeData new BinderProxyNativeData();nativeData-mOrgue new DeathRecipientList;nativeData-mObject val;jobject object env-CallStaticObjectMethod(gBinderProxyOffsets.mClass, gBinderProxyOffsets.mGetInstance, (jlong)nativeData, (jlong)val.get());...BinderProxyNativeData* actualNativeData getBPNativeData(env, object);if (actualNativeData nativeData){//Created a new Proxy...} else {delete nativeData;}return object;}
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ibinderForJavaObject()将java binder对象转换成native层binder对象javaObjectForIBinder()将native binder对象还原成java层binder对象。
总结
android在创建java层Binder对象和BinderProxy对象时会同时在native层创建对应的JavaBBinderHolder和BinderProxyNativeData。前者包含一个JavaBBinder类型的成员它继承自BBinder;后者包含BpBinder对象。这样就把java层和native层的连接建立起来了。 转自binder是如何在java层和native层实现统一的-腾讯云开发者社区-腾讯云
