1.简单介绍

MediaScannerJNI的在MediaScanner中的地位可參考
Android MediaScanner 总纲
MediaScanner JNI文件名称：
android_media_MediaScanner.cpp
位置：
frameworks\base\media\jni\android_media_MediaScanner.cpp
android_media_MediaScanner是JAVA层和server层沟通的一个桥梁

android_media_MediaScanner中有一个MyMediaScannerClient是一个调用JAVA层android/media/MediaScannerClient的入口是Native层想java层通信的桥梁。

2. 初始化

在MediaScanner.java初始化中过程调用，其核心是创建了一个StagefrightMediaScanner

static { System.loadLibrary("media_jni"); native_init(); } public MediaScanner(Context c) { native_setup(); ...... }

native_init 相应 android_media_MediaScanner_native_init
native_setup相应android_media_MediaScanner_native_setup

static voidandroid_media_MediaScanner_native_setup(JNIEnv *env, jobject thiz){ ALOGV("native_setup"); MediaScanner *mp = new StagefrightMediaScanner; ...... env->SetLongField(thiz, fields.context, (jlong)mp);}

3. android_media_MediaScanner_processDirectory

调用MediaScanner.cpp实现processDirectory完毕工作
在MediaScanner.java中调用scanDirectories。详见Android MediaScanner源码解析 第6节
其功能还是通过MediaScanner.cpp的processDirectory实现对

static voidandroid_media_MediaScanner_processDirectory( JNIEnv *env, jobject thiz, jstring path, jobject client){ MediaScanner *mp = getNativeScanner_l(env, thiz); ....... const char *pathStr = env->GetStringUTFChars(path, NULL); MyMediaScannerClient myClient(env, client); MediaScanResult result = mp->processDirectory(pathStr, myClient); env->ReleaseStringUTFChars(path, pathStr);}

4. android_media_MediaScanner_processFile

调用StageFrightMediaScanner.cpp实现processFile完毕工作

static voidandroid_media_MediaScanner_processFile( JNIEnv *env, jobject thiz, jstring path, jstring mimeType, jobject client){ // Lock already hold by processDirectory MediaScanner *mp = getNativeScanner_l(env, thiz); const char *pathStr = env->GetStringUTFChars(path, NULL); const char *mimeTypeStr = (mimeType ?
 env->GetStringUTFChars(mimeType, NULL) : NULL); ........ MyMediaScannerClient myClient(env, client); MediaScanResult result = mp->processFile(pathStr, mimeTypeStr, myClient); }

5. MyMediaScannerClient

引用android/media/MediaScannerClient中scanFile。handleStringTag。 setMimeType三个接口

 jclass mediaScannerClientInterface = env->FindClass(kClassMediaScannerClient); if (mediaScannerClientInterface == NULL) { ALOGE("Class %s not found", kClassMediaScannerClient); } else { mScanFileMethodID = env->GetMethodID( mediaScannerClientInterface, "scanFile", "(Ljava/lang/String;JJZZ)V"); mHandleStringTagMethodID = env->GetMethodID( mediaScannerClientInterface, "handleStringTag", "(Ljava/lang/String;Ljava/lang/String;)V"); mSetMimeTypeMethodID = env->GetMethodID( mediaScannerClientInterface, "setMimeType", "(Ljava/lang/String;)V"); }