第20课 在Android Native开发中加入新的C++类

​这节课我们开始利用ffmpeg和opencv在Android环境下来实现一个rtmp播放器，与第2课在PC端实现播放器的思路类似，只不过在处理音视频显示和播放的细节略有不同。

1.压缩备份上节课工程文件夹并修改工程文件夹为demo20，将demo20导入到Eclipse或者在原工程上继续下列的开发步骤。

2.右单击工程目录下的jni节点并添加一个新的C++类fmlp，如下图所示：

3.删除工程中的其它按钮，并添加id为startBtn的按钮：

在MainActivity.java中添加以下代码：

Button startBtn;

startBtn=(Button)findViewById(R.id.startBtn);                

public native String startFF(String rtmpURL);

public native String stopFF();

4.绑定单击事件start用于启动C++中的FFmpeg线程：

public void start(View view){ 

backWidth = Integer.toString(320);

          backHeight=Integer.toString(240);

rtmpURL = "rtmp://192.168.0.100/vod/2.mp4";

msgTxt.setText(startFF(rtmpURL));                

} 

5.在jni目录下添加fmlp类：

fmlp.h内容如下：

class fmlp {

public:

fmlp();

virtual ~fmlp();

string init();

};

fmlp.cpp内容如下：

std::stringfmlp::init() {

    return"Hello fmlp...";

}

6.在demo.cpp中添加启动FFmpeg的代码：

JNIEXPORT jstring JNICALL Java_com_example_demo_MainActivity_startFF(JNIEnv *env, jobject obj) {

if(myFmlp==NULL){

          myFmlp =new fmlp();

}

std::string str=myFmlp->init();

return env->NewStringUTF(str.c_str());

}

7.在Android.mk中添加fmlp编译选项以使fmlp.cpp被编译，完整的Android.mk内容如下

LOCAL_PATH := $(call my-dir)

#ffmpeg lib

include$(CLEAR_VARS)

LOCAL_MODULE := avcodec

LOCAL_SRC_FILES := lib/libavcodec.so

include$(PREBUILT_SHARED_LIBRARY)



include$(CLEAR_VARS)

LOCAL_MODULE := avdevice

LOCAL_SRC_FILES := lib/libavdevice.so

include$(PREBUILT_SHARED_LIBRARY)



include$(CLEAR_VARS)

LOCAL_MODULE := avfilter

LOCAL_SRC_FILES := lib/libavfilter.so

include$(PREBUILT_SHARED_LIBRARY)



include$(CLEAR_VARS)

LOCAL_MODULE := avformat

LOCAL_SRC_FILES := lib/libavformat.so

include$(PREBUILT_SHARED_LIBRARY)



include$(CLEAR_VARS)

LOCAL_MODULE := avutil

LOCAL_SRC_FILES := lib/libavutil.so

include$(PREBUILT_SHARED_LIBRARY)





include$(CLEAR_VARS)

LOCAL_MODULE := postproc

LOCAL_SRC_FILES := lib/libpostproc.so

include$(PREBUILT_SHARED_LIBRARY)



include$(CLEAR_VARS)

LOCAL_MODULE := swresample

LOCAL_SRC_FILES := lib/libswresample.so

include$(PREBUILT_SHARED_LIBRARY)



include$(CLEAR_VARS)

LOCAL_MODULE := swscale

LOCAL_SRC_FILES := lib/libswscale.so

include$(PREBUILT_SHARED_LIBRARY)



#x264 lib

include$(CLEAR_VARS)

LOCAL_MODULE := libx264

LOCAL_SRC_FILES := lib/libx264.161.so

include$(PREBUILT_SHARED_LIBRARY)



#opencv lib

include$(CLEAR_VARS)

LOCAL_MODULE := opencv

LOCAL_SRC_FILES :=lib/libopencv_java3.so

include$(PREBUILT_SHARED_LIBRARY)



#demo

include$(CLEAR_VARS)

LOCAL_MODULE    := demo

LOCAL_SRC_FILES := fmlp.cpp demo.cpp



LOCAL_C_INCLUDES += $(LOCAL_PATH)/include

##-landroid参数 for native windows

LOCAL_LDLIBS := -llog -landroid

#LOCAL_LDLIBS := -llog -lz

LOCAL_SHARED_LIBRARIES :=opencv libx264 avcodec avdevice avfilter avformat avutil postproc swresample swscale



include$(BUILD_SHARED_LIBRARY)

调试运行，能正确返回信息"Hello fmlp..."则表示程序运行正常。