Android MediaScannerJNI源代码具体解释

亦余心之所善兮，虽九死其犹未悔。这篇文章主要讲述Android MediaScannerJNI源代码具体解释相关的知识，希望能为你提供帮助。
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

文章图片

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。
Created with Rapha?l 2.1.0(java)MediaScanner(java)MediaScanner(native)android_media_MediaScanner(native)android_media_MediaScanner(C++)MediaScanner(C++)MediaScannermedia_jniMyMediaScannerClient2. 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 void android_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 void android_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 void android_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 ? 【Android MediaScannerJNI源代码具体解释】 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"); }