android传感器2--指南针

指南针的实现原理：
利用android的TYPE_ORIENTATION传感器和旋转动画实现指南针。
方向传感器的event.values是一个float类型的长度为3的数组。
float azimuth_angle = event.values[0];//在z轴旋转度
float pitch_angle = event.values[1];//在x轴旋转度
float roll_angle = event.values[2];//在y轴旋转度
根据api的解释：
Azimuth (degrees of rotation around the z axis). This is the angle between magnetic north and the device’s y axis. For example, if the device’s y axis is aligned with magnetic north this value is 0, and if the device’s y axis is pointing south this value is 180. Likewise, when the y axis is pointing east this value is 90 and when it is pointing west this value is 270.
这是磁北的夹角和设备的y轴。例如,如果设备的y轴与磁北这个值为0,如果设备的y轴指向南这个值是180。同样地,当y轴指向东指向西方时这个值是90,这个值是270。
Pitch (degrees of rotation around the x axis). This value is positive when the positive z axis rotates toward the positive y axis, and it is negative when the positive z axis rotates toward the negative y axis. The range of values is 180 degrees to -180 degrees.
值的范围是180度到-180度。
Roll (degrees of rotation around the y axis). This value is positive when the positive z axis rotates toward the positive x axis, and it is negative when the positive z axis rotates toward the negative x axis. The range of values is 90 degrees to -90 degrees.
值的范围是90度到-90度。

当手机水平放置时，图片旋转的度数就是-azimuth_angle

2.在主布局里放一张指南针的图片

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:paddingBottom="@dimen/activity_vertical_margin"android:orientation="vertical"android:paddingLeft="@dimen/activity_horizontal_margin"android:paddingRight="@dimen/activity_horizontal_margin"android:paddingTop="@dimen/activity_vertical_margin"tools:context="com.cindy.compass.MainActivity"><ImageView
        android:id="@+id/compass"android:layout_width="wrap_content"android:layout_height="wrap_content"android:src="@drawable/compass"/>
LinearLayout>

3.MainActivity.java

package com.cindy.compass;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.animation.Animation;
import android.view.animation.RotateAnimation;
import android.widget.ImageView;public class MainActivity extends AppCompatActivity implements SensorEventListener{private SensorManager sensorManager;private Sensor sensor_o;float degree = 0f;private float currentDegree = 0f;private ImageView imageView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);sensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);imageView = (ImageView)findViewById(R.id.compass);}@Overridepublic void onSensorChanged(SensorEvent event) {switch (event.sensor.getType()){case Sensor.TYPE_ORIENTATION:degree = event.values[0];float azimuth_angle = event.values[0];//在z轴旋转度float pitch_angle = event.values[1];//在x轴旋转度float roll_angle = event.values[2];//在y轴旋转度break;}/*RotateAnimation类：旋转变化动画类参数说明:fromDegrees：旋转的开始角度。toDegrees：旋转的结束角度。pivotXType：X轴的伸缩模式，可以取值为ABSOLUTE、RELATIVE_TO_SELF、RELATIVE_TO_PARENT。pivotXValue：X坐标的伸缩值。pivotYType：Y轴的伸缩模式，可以取值为ABSOLUTE、RELATIVE_TO_SELF、RELATIVE_TO_PARENT。pivotYValue：Y坐标的伸缩值*/RotateAnimation ra = new RotateAnimation(currentDegree,-degree,Animation.RELATIVE_TO_SELF,0.5f,Animation.RELATIVE_TO_SELF,0.5f);ra.setDuration(200);imageView.startAnimation(ra);currentDegree = -degree;}@Overridepublic void onAccuracyChanged(Sensor sensor, int accuracy) {}@Overrideprotected void onResume() {super.onResume();sensor_o = sensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);sensorManager.registerListener(this, sensor_o, SensorManager.SENSOR_DELAY_NORMAL);//注册指南针传感器的监听器}@Overrideprotected void onPause() {super.onPause();sensorManager.unregisterListener(this, sensor_o);//注销传感器}
}

应用程序下载地址：android指南针

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