14

我正在尝试使用加速度计和磁场传感器对 Android 指南针进行编程，现在我想知道如何为我的指南针获取正确的角度。

我分别在“加速度”和“磁力”中读取加速度计和磁场传感器的值。为了获得角度，我执行以下操作：

float R[] = new float[9];
float I[] = new float[9];
boolean success = SensorManager.getRotationMatrix(R, I, accele, magne);
        if(success) {
            float orientation[] = new float[3];
            SensorManager.getOrientation(R, orientation);
            azimuth = orientation[0]; // contains azimuth, pitch, roll
                            ....

稍后，我使用旋转矩阵来放置我的针：

rotation.setRotate(azimuth, compass.getWidth() / 2, compass.getHeight() / 2);
canvas.drawBitmap(needle, rotation, null);

现在，getOrientation 的文档说，orientation[0] 应该是围绕 z 轴的旋转。TYPE_ORIENTATION 的文档指出“方位角，磁北方向和 y 轴之间的角度，围绕 z 轴（0 到 359）。0=北，90=东，180=南，270=西”。

然而，我的方位角不在 0 到 359 之间，而是在 -2 到 2 之间。getOrientation 的方位角到底是什么？如何将其转换为角度？

4

3 回答 3

21

使用以下以弧度 (-PI, +PI) 为单位的给定方位角转换为度数 (0, 360)

float azimuthInRadians = orientation[0];
float azimuthInDegress = (float)Math.toDegrees(azimuthInRadians);
if (azimuthInDegress < 0.0f) {
    azimuthInDegress += 360.0f;
}

为方便起见使用的变量名 ;-)

于 2012-11-08T17:21:46.643 回答
8

可以从https://github.com/iutinvg/compass获取代码片段

它不使用过时的东西，应用低通滤波器。

于 2012-12-07T09:59:49.097 回答
2

我在谷歌的 ApiDemos 中找到了这个：

    /*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.apis.graphics;

import android.app.Activity;
import android.content.Context;
import android.graphics.*;
import android.hardware.SensorListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;
import android.util.Config;
import android.util.Log;
import android.view.View;

public class Compass extends GraphicsActivity {

    private static final String TAG = "Compass";

    private SensorManager mSensorManager;
    private SampleView mView;
    private float[] mValues;

    private final SensorListener mListener = new SensorListener() {

        public void onSensorChanged(int sensor, float[] values) {
            if (Config.LOGD) Log.d(TAG, "sensorChanged (" + values[0] + ", " + values[1] + ", " + values[2] + ")");
            mValues = values;
            if (mView != null) {
                mView.invalidate();
            }
        }

        public void onAccuracyChanged(int sensor, int accuracy) {
            // TODO Auto-generated method stub

        }
    };

    @Override
    protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        mSensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);
        mView = new SampleView(this);
        setContentView(mView);
    }

    @Override
    protected void onResume()
    {
        if (Config.LOGD) Log.d(TAG, "onResume");
        super.onResume();
        mSensorManager.registerListener(mListener, 
                SensorManager.SENSOR_ORIENTATION,
                SensorManager.SENSOR_DELAY_GAME);
    }

    @Override
    protected void onStop()
    {
        if (Config.LOGD) Log.d(TAG, "onStop");
        mSensorManager.unregisterListener(mListener);
        super.onStop();
    }

    private class SampleView extends View {
        private Paint   mPaint = new Paint();
        private Path    mPath = new Path();
        private boolean mAnimate;
        private long    mNextTime;

        public SampleView(Context context) {
            super(context);

            // Construct a wedge-shaped path
            mPath.moveTo(0, -50);
            mPath.lineTo(-20, 60);
            mPath.lineTo(0, 50);
            mPath.lineTo(20, 60);
            mPath.close();
        }

        @Override protected void onDraw(Canvas canvas) {
            Paint paint = mPaint;

            canvas.drawColor(Color.WHITE);

            paint.setAntiAlias(true);
            paint.setColor(Color.BLACK);
            paint.setStyle(Paint.Style.FILL);

            int w = canvas.getWidth();
            int h = canvas.getHeight();
            int cx = w / 2;
            int cy = h / 2;

            canvas.translate(cx, cy);
            if (mValues != null) {            
                canvas.rotate(-mValues[0]);
            }
            canvas.drawPath(mPath, mPaint);
        }

        @Override
        protected void onAttachedToWindow() {
            mAnimate = true;
            super.onAttachedToWindow();
        }

        @Override
        protected void onDetachedFromWindow() {
            mAnimate = false;
            super.onDetachedFromWindow();
        }
    }
}

如您所见，您确实获得了 0 到 360 之间的度数

于 2012-11-08T16:56:43.730 回答