android传感器

In this tutorial, we’ll be digging deep into the world of Android Sensors. Our smartphones are much more than just speed, UI and animations.

在本教程中，我们将深入研究Android传感器的世界。 我们的智能手机不仅限于速度，UI和动画。

Android传感器 (Android Sensors)

Android Sensors contains properties to detect changes in the environment such as light, proximity, rotation, movements, magnetic fields and much more.

Android Sensors包含可检测环境变化的属性，例如光线，接近度，旋转，运动，磁场等。

Broadly speaking, the Android Sensors fall under the following categories:

从广义上讲，Android传感器属于以下类别：

• Environment Sensors
  环境传感器
• Motion Sensors
  运动传感器
• Orientation and Position Sensors
  方向和位置传感器

To access the various Sensors in Android, you must use the SensorManager class.

要访问Android中的各种Sensor，必须使用SensorManager类。

Following code shows how to initialize a SensorManager:

以下代码显示了如何初始化SensorManager ：

SensorManager sensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);

Next, you can use the Sensor class to instantiate the specific Sensor.

接下来，您可以使用Sensor类来实例化特定的Sensor。

Sensor lightSensor = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);

Next, you can register the sensor using the following code:

接下来，您可以使用以下代码注册传感器：

sensorManager.registerListener(this, lightSensor,
                SensorManager.SENSOR_DELAY_NORMAL);

It’s recommended to register the listener in the onResume() method and unregister it in the onPause method in order to save battery power.

建议您在onResume()方法中注册侦听器，然后在onPause方法中取消注册侦听器，以节省电池电量。

In order to listen to sensor events, you can implement the SensorEventListener interface in the activity.

为了监听传感器事件，您可以在活动中实现SensorEventListener接口。

You need to override the following methods for that:

您需要为此重写以下方法：

@Override
    public void onSensorChanged(SensorEvent event) {
        
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {

    }

To get a list of all the available sensors on the device, use the following code:

要获取设备上所有可用传感器的列表，请使用以下代码：

List<Sensor> sensorList = sensorManager.getSensorList(Sensor.TYPE_ALL);

String sensorInfo = "";
for (Sensor s : sensorList){
    sensorInfo= sensorInfo + s.getName()+ "\n";
}

In the next section, we’ll discuss some of the common types of Sensors.

在下一节中，我们将讨论一些常见的传感器类型。

Android传感器类型 (Android Sensors Types)

• Photometer is used to sense and control the brightness. Besides, there are sensors for pressure, humidity, and temperature.
  光度计用于感应和控制亮度。 此外，还有压力，湿度和温度传感器。
• For movements, Accelerometer is used to detect shakes/tilt gestures.
  对于运动， 加速度计用于检测摇动/倾斜手势。
• Proximity Sensors are used to detect how close the object is to the device. It’s commonly present in Call Applications. As you bring the phone close to the ear, the screen goes black, thanks to this sensor. Though the maximum range of proximity is 5 cms.
  接近传感器用于检测物体与设备的距离。 它通常出现在呼叫应用程序中。 当您将手机靠近耳朵时，借助此传感器，屏幕会变黑。 虽然最大接近范围是5厘米。
• Gyroscope is used to measure rotation/spin. Gravity sensors are used to measure the force of gravity.
  陀螺仪用于测量旋转/旋转。 重力传感器用于测量重力。
• Magneto Meter is used to get the device position.
  磁力仪用于获取设备位置。
• Pedometer is used to detect the number of steps the user takes.
  计步器用于检测用户执行的步数。

Following image depicts a few sensor types and their event data values with the respective formats.

下图描绘了几种传感器类型及其事件数据值以及相应的格式。

如何检查Android Sensor是否可用？ (How to Check if Android Sensor is Available?)

Some devices don’t support certain Sensors. So you can simply add the permissions in the Manifest file.
Google ensures that the Application on the Play store would not be visible to users with unsupported devices.

某些设备不支持某些传感器。 因此，您只需在清单文件中添加权限。
Google确保Play商店中的应用程序对于不支持设备的用户不可见。

<uses-feature android:name="android.hardware.accelerometer"
    android:required="true" />

<uses-feature android:name="android.hardware.sensor.proximity"
    android:required="true" />

<uses-feature android:name="android.hardware.sensor.gyroscope"
    android:required="true" />

In the next section, we’ll implement certain sensors in our Android Application.

在下一部分中，我们将在Android应用程序中实现某些传感器。

Android传感器示例项目结构 (Android Sensors Example Project Structure)

Android传感器示例代码 (Android Sensors Example Code)

The code for the activity_main.xml is given below:

下面给出了activity_main.xml的代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:app="https://schemas.android.com/apk/res-auto"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_gravity="center"
    android:layout_margin="16dp"
    android:gravity="center"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btnAccelerometer"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="accelerometerSensorOnClick"
        android:text="Accelerometer" />


    <Button
        android:id="@+id/btnProximity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="proximitySensorOnClick"
        android:text="Proximity Sensor" />


    <Button
        android:id="@+id/btnGyro"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="gyroscopeSensorOnClick"
        android:text="Gyroscope" />


    <Button
        android:id="@+id/btnLightSensor"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="lightSensorOnClick"
        android:text="Light Sensor" />


    <Button
        android:id="@+id/btnStepCounterOnClick"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="stepCounterOnClick"
        android:text="Step Counter Sensor" />

    <Button
        android:id="@+id/btnAmbientTemp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="ambientTempSensorOnClick"
        android:text="Ambient Temperature Sensor" />


    <TextView
        android:id="@+id/tvResult"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="Values would be entered here..." />

</LinearLayout>

The code for the MainActivity.java is given below:

MainActivity.java的代码如下：

package com.journaldev.androidsensors;

import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements SensorEventListener {

    private TextView textView;

    private SensorManager sensorManager;

    private Sensor accelerometerSensor;
    private Sensor proximitySensor;
    private Sensor lightSensor;
    private Sensor stepCounterSensor;
    private Sensor tempSensor;
    private Sensor gyroscopeSensor;

    private int currentSensor;

    private long lastUpdate = 0;
    private float last_x, last_y, last_z;
    private static final int SHAKE_THRESHOLD = 600;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView = findViewById(R.id.tvResult);

        sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);

        accelerometerSensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        proximitySensor = sensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY);
        lightSensor = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
        stepCounterSensor = sensorManager.getDefaultSensor(Sensor.TYPE_STEP_DETECTOR);
        gyroscopeSensor = sensorManager.getDefaultSensor(Sensor.TYPE_GYROSCOPE);
        tempSensor = sensorManager.getDefaultSensor(Sensor.TYPE_AMBIENT_TEMPERATURE);
    }


    public boolean checkSensorAvailability(int sensorType) {
        boolean isSensor = false;
        if (sensorManager.getDefaultSensor(sensorType) != null) {
            isSensor = true;
        }
        return isSensor;
    }

    @Override
    public void onSensorChanged(SensorEvent event) {

        if (event.sensor.getType() == currentSensor) {

            if (currentSensor == Sensor.TYPE_LIGHT) {
                float valueZ = event.values[0];
                textView.setText("Brightness " + valueZ);
            } else if (currentSensor == Sensor.TYPE_PROXIMITY) {
                float distance = event.values[0];
                textView.setText("Proximity " + distance);
            } else if (currentSensor == Sensor.TYPE_STEP_DETECTOR) {
                float steps = event.values[0];
                textView.setText("Steps : " + steps);
            } else if (currentSensor == Sensor.TYPE_ACCELEROMETER) {
                float x = event.values[0];
                float y = event.values[1];
                float z = event.values[2];

                long curTime = System.currentTimeMillis();

                if ((curTime - lastUpdate) > 100) {
                    long diffTime = (curTime - lastUpdate);
                    lastUpdate = curTime;

                    float speed = Math.abs(x + y + z - last_x - last_y - last_z) / diffTime * 10000;

                    if (speed > SHAKE_THRESHOLD) {
                        Toast.makeText(getApplicationContext(), "Your phone just shook", Toast.LENGTH_LONG).show();
                    }

                    last_x = x;
                    last_y = y;
                    last_z = z;
                }
            } else if (currentSensor == Sensor.TYPE_GYROSCOPE) {
                if (event.values[2] > 0.5f) {
                    textView.setText("Anti Clock");
                } else if (event.values[2] < -0.5f) {
                    textView.setText("Clock");
                }
            } else if (currentSensor == Sensor.TYPE_AMBIENT_TEMPERATURE) {
                textView.setText("Ambient Temp in Celsius :" + event.values[0]);
            }

        }

    }


    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {

    }


    public void accelerometerSensorOnClick(View view) {
        if (checkSensorAvailability(Sensor.TYPE_ACCELEROMETER)) {
            currentSensor = Sensor.TYPE_ACCELEROMETER;
        }
        textView.setText("Accelerometer not available");
    }

    public void proximitySensorOnClick(View view) {
        if (checkSensorAvailability(Sensor.TYPE_PROXIMITY)) {
            currentSensor = Sensor.TYPE_PROXIMITY;
        }
        textView.setText("Proximity Sensor not available");
    }

    public void gyroscopeSensorOnClick(View view) {
        if (checkSensorAvailability(Sensor.TYPE_GYROSCOPE)) {
            currentSensor = Sensor.TYPE_GYROSCOPE;
        } else {
            textView.setText("Gyroscope Sensor not available");
        }
    }

    public void lightSensorOnClick(View view) {
        if (checkSensorAvailability(Sensor.TYPE_LIGHT)) {
            currentSensor = Sensor.TYPE_LIGHT;
        } else {
            textView.setText("Light Sensor not available");
        }
    }


    public void stepCounterOnClick(View view) {
        if (checkSensorAvailability(Sensor.TYPE_STEP_DETECTOR)) {
            currentSensor = Sensor.TYPE_STEP_DETECTOR;
        } else {
            textView.setText("Step Counter Sensor not available");
        }
    }

    public void ambientTempSensorOnClick(View view) {
        if (checkSensorAvailability(Sensor.TYPE_AMBIENT_TEMPERATURE)) {
            currentSensor = Sensor.TYPE_AMBIENT_TEMPERATURE;
        } else {
            textView.setText("Ambient Temperature Sensor not available");
        }
    }

    @Override
    protected void onResume() {
        super.onResume();

        sensorManager.registerListener(this, accelerometerSensor,
                SensorManager.SENSOR_DELAY_NORMAL);
        sensorManager.registerListener(this, lightSensor,
                SensorManager.SENSOR_DELAY_NORMAL);
        sensorManager.registerListener(this, proximitySensor,
                SensorManager.SENSOR_DELAY_NORMAL);
        sensorManager.registerListener(this, stepCounterSensor,
                SensorManager.SENSOR_DELAY_NORMAL);
        sensorManager.registerListener(this, tempSensor,
                SensorManager.SENSOR_DELAY_NORMAL);
        sensorManager.registerListener(this, gyroscopeSensor,
                SensorManager.SENSOR_DELAY_NORMAL);
    }

    @Override
    protected void onPause() {
        super.onPause();
        sensorManager.unregisterListener(this);
    }


}

For the accelerometer, we need to get the position of all the three coordinates from each of the three axes. The accelerometer is so sensitive that it keeps updating these points.

对于加速度计，我们需要从三个轴中的每个轴获取所有三个坐标的位置。 加速度计非常灵敏，因此会不断更新这些点。

In order to detect whether it’s a shake or not, we take the difference of the points within a given time frame to detect how quickly they moved.

为了检测是否晃动，我们采用给定时间范围内的点差来检测它们移动的速度。

The gyroscope detects whether the phone is rotated anticlockwise or clockwise in the z plane.

陀螺仪检测手机在z平面中是逆时针方向还是顺时针方向旋转。

The output of the above application in action is given below. Since we cannot show a live demo, we’ve just displayed the sensor value for brightness.

下面给出了上面应用程序的输出。 由于我们无法显示实时演示，因此我们只显示了亮度的传感器值。

That brings an end to this android sensors tutorial. You can download the project from the link below.

这结束了本android传感器教程。 您可以从下面的链接下载项目。

翻译自: https://www.journaldev.com/25691/android-sensors

android传感器