Introduction to Sensors
介紹傳感器
The Android sensor framework lets you access many types of sensors. Some of these sensors
are hardware-based and some are software-based. Hardware-based sensors are physical components built into a handset or tablet device. They derive their data by directly measuring specific environmental properties, such as acceleration, geomagnetic field strength, or angular change. Software-based sensors are not physical devices, although they mimic hardware-based sensors. Software-based sensors derive their data from one or more of the hardware-based sensors and are sometimes called virtual sensors or synthetic sensors. The linear acceleration sensor and the gravity sensor are examples of software-based sensors.
Android sensor framework 讓你使用多種傳感器。有基於硬件和基於軟件的。基於硬件的傳感器是內置於設備中的物理組件。它們直接測量具體的環境屬性來得出數據，例如加速度，地磁場強度，或者角的變化。基於軟件的傳感器你不是物理設備，儘管它們模擬硬件傳感器。軟件探測器通過一個或者多個硬件傳感器來得出數據，有時稱爲虛擬傳感器或者合成傳感器。線性加速度傳感器和重力傳感器是軟件傳感器的例子。
Table 1 summarizes the sensors that are supported by the Android platform.
表1 總結了android 平臺支持的傳感器。
Few Android-powered devices have every type of sensor. For example, most handset devices and tablets have an accelerometer and a magnetometer, but fewer devices have barometers or thermometers. Also, a device can have more than one sensor of a given type. For example, a device can have two gravity sensors, each one having a different range.
少有android 設備每種傳感器都有。例如，大部分手機設備和平板有一個加速計和一個磁力計，但是較少設備有氣壓計或溫度計。一個設備也可以有一個以上的同類傳感器，如果可以用兩個不同範圍的重力傳感器。
Table 1. Sensor types supported by the Android platform.
表1。Android 平臺支持的傳感器種類。
| Sensor | Type | Description | Common Uses |
|---|---|---|---|
TYPE_ACCELEROMETER | Hardware | Measures the acceleration force inm/s2 that is applied to a device on all three physical axes (x, y, and z), including the force of gravity. 測量在設備的三個軸的加速度，單位 m/s2 ，包括重力加速度 | Motion detection (shake, tilt, etc.). 運動檢測 |
TYPE_AMBIENT_TEMPERATURE | Hardware | Measures the ambient room temperature in degrees Celsius (°C). See note below. 測量室溫，單位攝氏度(°C) | Monitoring air temperatures. 監視空氣溫度 |
TYPE_GRAVITY | Software or Hardware | Measures the force of gravity in m/s2 that is applied to a device on all three physical axes (x, y, z). 測量在設備三個軸的重力加速度，單位m/s2 。 | Motion detection (shake, tilt, etc.). |
TYPE_GYROSCOPE | Hardware | Measures a device's rate of rotation in rad/s around each of the three physical axes (x, y, and z). 測量在設備三個軸上的角速度。單位rad/s | Rotation detection (spin, turn, etc.). 旋轉檢測 |
TYPE_LIGHT | Hardware | Measures the ambient light level (illumination) in lx. 測試環境亮度級，單位 lx | Controlling screen brightness. 控制屏幕亮度 |
TYPE_LINEAR_ACCELERATION | Software or Hardware | Measures the acceleration force in m/s2 that is
applied to a device on all three physical axes (x, y, and z), excluding the force of gravity. 測量在設備三軸上的加速度，排除了重力。 | Monitoring acceleration along a single axis. 檢測一個軸上的加速度 |
TYPE_MAGNETIC_FIELD | Hardware | Measures the ambient geomagnetic field for all three physical axes (x, y, z) in μT. 測量三軸的地磁場，單位μT | Creating a compass. 創建一個羅盤 |
TYPE_ORIENTATION | Software | Measures degrees of rotation that a device makes around all three physical axes (x, y, z).As of API level 3 you can obtain the inclination matrix and rotation matrix for
a device by using the gravity sensor and the geomagnetic field sensor in conjunction with the 測量設備繞三軸轉的旋轉度。 | Determining device position. |
TYPE_PRESSURE | Hardware | Measures the ambient air pressure in hPa or mbar.測量氣壓 | Monitoring air pressure changes. |
TYPE_PROXIMITY | Hardware | Measures the proximity of an object in cm relative to the view screen of a device. This sensor is typically used to determine whether a handset is being held up to a person's ear. | Phone position during a call. |
TYPE_RELATIVE_HUMIDITY | Hardware | Measures the relative ambient humidity in percent (%). | Monitoring dewpoint, absolute, and relative humidity. |
TYPE_ROTATION_VECTOR | Software or Hardware | Measures the orientation of a device by providing the three elements of the device's rotation vector. | Motion detection and rotation detection. |
TYPE_TEMPERATURE | Hardware | Measures the temperature of the device in degrees Celsius (°C). This sensor
implementation varies across devices and
this sensor was replaced with the TYPE_AMBIENT_TEMPERATURE sensor in
API Level 14 | Monitoring temperatures. |