Android底层字符传递给上层应用举例

1、Android的硬件抽象层读取相应的串口设备的数据：
static int uart_read_drv(struct uart_control_device_t *dev, char *buf, int count)

        {

                int count1 = 0;

                count1 = read(fd, buf, count);

                if(count1 < 0)

                {

                        perror("read");

                }

                return 0;

        }
2、 Android的JNI层经过回调之后，可以通过自定义的相应的结构体方法读取到硬件抽象层的数据，并反馈到上层：
static jchar uart_read(JNIEnv* env, jobject thiz) {

                char s_buf[100]={0};

                if (sUartDevice) {

                        sUartDevice->uart_read_hal(sUartDevice, s_buf, 1);

                }else{

                        LOGI("sUartDevice is null");

                }

                if (s_buf == 0)

                LOGI("JNI: Lost info");

                else

                {

                        LOGI("***********JNI:info length is : %d", strlen(s_buf));

                }

                return s_buf[0];

        }
3、Android的JNI和上层函数的对应描述：
static const JNINativeMethod gMethods[] = {

        ….

        { "_uart_data_update",

                "()C",

                (void*)uart_read },

                ….

        };
4、Android的Framework层定义相应的本地接口方法：
private static native char _uart_data_update();
通过类的方法进行封装：

        public class Uart {

                static {

                System.loadLibrary("uart_runtime");

                Log.i("**********************Java Service", "loadLibrary sucess");

                }

                 public Uart(){

                        _init();

                }

                public char GpsDataUpdate() {

                char s = _uart_data_update();

                        return s;

                }

                private static native boolean _init();

                private static native char _uart_data_update();

                 }
}
5、.Java上层App进行调用，并获得数据：
static Uart uartuart = new Uart();

        char s = uartuart.GpsDataUpdate();