Android MediaScannerJNI源代碼具體解釋
1.簡單介紹
MediaScannerJNI的在MediaScanner中的地位可參考
Android MediaScanner 總綱
MediaScanner JNI文件名稱:
android_media_MediaScanner.cpp
位置:
frameworks\base\media\jni\android_media_MediaScanner.cpp
android_media_MediaScanner是JAVA層和server層溝通的一個橋梁
android_media_MediaScanner中有一個MyMediaScannerClient是一個調用JAVA層android/media/MediaScannerClient的入口是Native層想java層通信的橋梁。
2. 初始化
在MediaScanner.java初始化中過程調用,其核心是創建了一個StagefrightMediaScanner
static {
System.loadLibrary("media_jni" );
native_init();
}
public MediaScanner(Context c) {
native_setup();
......
}
native_init 相應 android_media_MediaScanner_native_init
native_setup相應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
調用MediaScanner.cpp實現processDirectory完畢工作
在MediaScanner.java中調用scanDirectories。詳見Android MediaScanner源碼解析 第6節
其功能還是通過MediaScanner.cpp的processDirectory實現對
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
調用StageFrightMediaScanner.cpp實現processFile完畢工作
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 ? 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三個接口
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");
}
Android MediaScannerJNI源代碼具體解釋