Question

我已经使用NDK更快地搜索了关于轮询加速度计的教程/答案，但还没有找到求解器。刚刚找到了androiddevelopers文档here。

我需要的是轮询加速度大约每秒100个样本（100Hz），默认情况下我的设备（三星Galaxy SL i9003与姜饼2.3.5）默认SENSOR_DELAY_FASTEST只能获得大约60个样本persecond（60Hz）。因此，我尝试通过生成.c文件，通过NativeActivity访问传感器，我尝试根据sensor.h和looper.h制作。

#include <jni.h>
#include <string.h>

#include <android/sensor.h>
#include <android/log.h>
#include <android/looper.h>

#define TAG "accelerondk"
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, TAG, __VA_ARGS__)
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, TAG, __VA_ARGS__)

#define LOOPER_ID 1
#define SAMP_PER_SEC 100 //i've changed to 120, even 10, but nothing happen

void Java_azka_web_ndk_AcceleroNDKActivity_startMonitoring(JNIEnv* env, jclass clazz) {
    ASensorManager* sensorManager = ASensorManager_getInstance();

    ALooper* looper = ALooper_forThread();
    if(looper == NULL)
        looper = ALooper_prepare(ALOOPER_PREPARE_ALLOW_NON_CALLBACKS);

    ASensorRef accelerometerSensor = ASensorManager_getDefaultSensor(sensorManager,ASENSOR_TYPE_ACCELEROMETER);
    LOGI("accelerometerSensor: %s, vendor: %s", ASensor_getName(accelerometerSensor), ASensor_getVendor(accelerometerSensor));

    ASensorEventQueue* queue = ASensorManager_createEventQueue(sensorManager, looper, LOOPER_ID, NULL, NULL);

    ASensorEventQueue_enableSensor(queue, accelerometerSensor);
    ASensorEventQueue_setEventRate(queue, accelerometerSensor, (1000L/SAMP_PER_SEC)*1000); 

    int ident;//identifier 
    int events;
    while (1) {
        while ((ident=ALooper_pollAll(-1, NULL, &events, NULL) >= 0)) {
            // If a sensor has data, process it now.
            if (ident == LOOPER_ID) {
                ASensorEvent event;
                while (ASensorEventQueue_getEvents(queue, &event, 1) > 0) {
                    LOGI("aaaaaaa accelerometer X = %f y = %f z=%f ", event.acceleration.x, event.acceleration.y, event.acceleration.z);
                }
            }
        }
    }

}

到目前为止，我已经能够使用NativeActivity访问加速度计，但是采样数量没有变化。即使我改变ASensorEventQueue_setEventRate足够大或足够小，加速记录的速度仍然是每秒约60个样本（每15个样本1个样本）

我的代码有错误吗？或者我忘了的东西？

提前致谢

Answer 1

我还尝试了传感器的采样率。我使用的是Galaxy Nexus。如果我只使用Acc-Sensor，频率非常低（大约40Hz），但如果我使用Acc-Sensor加上磁性和陀螺仪传感器，每个传感器的采样率约为100Hz。我没有解释为什么会这样。另一个观察结果是传递给ASensorEventQueue_setEventRate的值无效。采样率始终相同。 SDK-Code的行为完全相同。

以下是我用于基准测试的代码：

#include <string.h>
#include <jni.h>
#include <android/sensor.h>
#include <android/looper.h>
#include <android/log.h>
#include <time.h>
#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "TestJNIActivity", __VA_ARGS__))
#define LOOPER_ID 1
#define SAMP_PER_SEC 100

ASensorEventQueue* sensorEventQueue;

int accCounter = 0;
int64_t lastAccTime = 0;

int gyroCounter = 0;
int64_t lastGyroTime = 0;

int magCounter = 0;
int64_t lastMagTime = 0;

/* This is a trivial JNI example where we use a native method
 * to return a new VM String. See the corresponding Java source
 * file located at:
 *
 *   apps/samples/hello-jni/project/src/com/example/HelloJni/HelloJni.java
 */

static int get_sensor_events(int fd, int events, void* data);

struct tm* start;
struct tm* finish;


jstring
Java_de_tum_ndktest_TestJNIActivity_stringFromJNI( JNIEnv* env, jobject thiz )
{
    LOGI("stringFromJNI");
    return (*env)->NewStringUTF(env,"Hello from JNI !");
}

void
Java_de_tum_ndktest_TestJNIActivity_sensorValue( JNIEnv* env, jobject thiz ) {

    ASensorEvent event;
    int events, ident;
    ASensorManager* sensorManager;
    const ASensor* accSensor;
    const ASensor* gyroSensor;
    const ASensor* magSensor;
    void* sensor_data = malloc(1000);

    LOGI("sensorValue() - ALooper_forThread()");

    ALooper* looper = ALooper_forThread();

    if(looper == NULL)
    {
        looper = ALooper_prepare(ALOOPER_PREPARE_ALLOW_NON_CALLBACKS);
    }

    sensorManager = ASensorManager_getInstance();

    accSensor = ASensorManager_getDefaultSensor(sensorManager, ASENSOR_TYPE_ACCELEROMETER);
    gyroSensor = ASensorManager_getDefaultSensor(sensorManager, ASENSOR_TYPE_GYROSCOPE);
    magSensor = ASensorManager_getDefaultSensor(sensorManager, ASENSOR_TYPE_MAGNETIC_FIELD);



    sensorEventQueue = ASensorManager_createEventQueue(sensorManager, looper, 3, get_sensor_events, sensor_data);

    ASensorEventQueue_enableSensor(sensorEventQueue, accSensor);
    ASensorEventQueue_enableSensor(sensorEventQueue, gyroSensor);
    ASensorEventQueue_enableSensor(sensorEventQueue, magSensor);

    //Sampling rate: 100Hz
    int a = ASensor_getMinDelay(accSensor);
    int b = ASensor_getMinDelay(gyroSensor);
    int c = ASensor_getMinDelay(magSensor);
    LOGI("min-delay: %d, %d, %d",a,b,c);
    ASensorEventQueue_setEventRate(sensorEventQueue, accSensor, 100000);
    ASensorEventQueue_setEventRate(sensorEventQueue, gyroSensor, 100000);
    ASensorEventQueue_setEventRate(sensorEventQueue, magSensor, 100000);

    LOGI("sensorValue() - START");
}



static int get_sensor_events(int fd, int events, void* data) {
  ASensorEvent event;
  //ASensorEventQueue* sensorEventQueue;
  while (ASensorEventQueue_getEvents(sensorEventQueue, &event, 1) > 0) {
        if(event.type == ASENSOR_TYPE_ACCELEROMETER) {
                //LOGI("accl(x,y,z,t): %f %f %f %lld", event.acceleration.x, event.acceleration.y, event.acceleration.z, event.timestamp);
                if(accCounter == 0 || accCounter == 1000)
                    {
                     LOGI("Acc-Time: %lld (%f)", event.timestamp,((double)(event.timestamp-lastAccTime))/1000000000.0);
                     lastAccTime = event.timestamp;
                     accCounter = 0;
                    }

                accCounter++;
        }
        else if(event.type == ASENSOR_TYPE_GYROSCOPE) {
                //LOGI("accl(x,y,z,t): %f %f %f %lld", event.acceleration.x, event.acceleration.y, event.acceleration.z, event.timestamp);
                if(gyroCounter == 0 || gyroCounter == 1000)
                    {

                     LOGI("Gyro-Time: %lld (%f)", event.timestamp,((double)(event.timestamp-lastGyroTime))/1000000000.0);
                     lastGyroTime = event.timestamp;
                     gyroCounter = 0;
                    }

                gyroCounter++;
        }
        else if(event.type == ASENSOR_TYPE_MAGNETIC_FIELD) {
                //LOGI("accl(x,y,z,t): %f %f %f %lld", event.acceleration.x, event.acceleration.y, event.acceleration.z, event.timestamp);
                if(magCounter == 0 || magCounter == 1000)
                    {
                     LOGI("Mag-Time: %lld (%f)", event.timestamp,((double)(event.timestamp-lastMagTime))/1000000000.0);
                     lastMagTime = event.timestamp;
                     magCounter = 0;
                    }

                magCounter++;
        }

  }
  //should return 1 to continue receiving callbacks, or 0 to unregister
  return 1;
}

Answer 2

问题有点陈旧但是这两篇文章可能会帮助那些偶然发现这个问题的人，并想知道为什么会这么麻烦，或者如何优化NDK中的例子。

这两篇简短的文章列出了问题和潜在的解决方案（但没有完整的源解决方案）

Java interfaced sensor performance

Native Sampling Improvement

Answer 3

这是一个老问题，但由于缺乏文档和文章，我想我会分享我的经验。我在Nexus 5X上完成了所有测试。您的设备可能不同。

原始代码看起来正确。从文档中可以明显看出，您只能在启用传感器之后设置事件率，并且...

如果您重新启用传感器（例如，在onPause（）和onResume（）之后），则需要再次设置事件速率。如果您有＆＃34;双启用＆＃ 34;就像我在我的代码中所做的那样（init（）中的enable（）/ setEventRate（），但只有onResume（）中的enable（）），你将得到默认的轮询率。

Answer 4

您可能受限于设备中加速度计硬件的速度。但是，您可以使用interpolation来获取一些额外的数据点。

通过NativeActivity NDK访问（更快的轮询）加速度计

4 个答案: