Android MediaScannerJNI源码详解
1.简介
MediaScannerJNI的在MediaScanner中的地位可参考
Android MediaScanner 总纲
MediaScanner JNI文件名:
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 对应 android_media_MediaScanner_native_init
native_setup对应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完成工作
在MediaScanner.java中调用scanDirectories,详见Android MediaScanner源代码解析 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完成工作
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"); }
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