Androidのセンサーを使って端末の向き(縦横)を判定する

MainActivity.java

package com.voidroider.sensorsample;

import android.app.Activity;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends Activity implements SensorEventListener {

    /**
     * 回転したと判定する際の閾値角度
     */
    private static final int THRESHOLD_DEGREE = 60;
    /**
     * 縦から横に変化したと判定する際の角度
     */
    private static final int VERTICAL_TO_HORIZONTAL_DEGREE = THRESHOLD_DEGREE;
    /**
     * 横から縦にに変化したと判定する際の角度
     */
    private static final int HORIZONTAL_TO_VERTICAL_DEGREE = 90 - THRESHOLD_DEGREE;
    /**
     * 縦向きを表す定数
     */
    private static final int ORIENTATION_VERTICAL = 0;
    /**
     * 横向きを表す定数
     */
    private static final int ORIENTATION_HORIZONTAL = 1;
    /**
     * ラジアンを度に変換する際の定数
     */
    protected final static double RAD2DEG = 180 / Math.PI;

    private static final int MATRIX_SIZE = 16;

    /* 回転行列 */
    float[] inR = new float[MATRIX_SIZE];
    float[] outR = new float[MATRIX_SIZE];
    float[] I = new float[MATRIX_SIZE];

    float[] orientationValues = new float[3];
    float[] magneticValues = new float[3];
    float[] accelerometerValues = new float[3];

    private int mPreOrientation = -1;
    SensorManager sensorManager;

    TextView azimuthText;
    TextView pitchText;
    TextView rollText;
    TextView orientationText;

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

        findViews();
        initSensor();
    }

    public void onResume() {
        super.onResume();
        sensorManager.registerListener(
                this,
                sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
                SensorManager.SENSOR_DELAY_UI);
        sensorManager.registerListener(
                this,
                sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD),
                SensorManager.SENSOR_DELAY_UI);
    }

    public void onPause() {
        super.onPause();
        sensorManager.unregisterListener(this);
    }

    protected void findViews() {
        azimuthText = (TextView) findViewById(R.id.azimuth);
        pitchText = (TextView) findViewById(R.id.pitch);
        rollText = (TextView) findViewById(R.id.roll);
        orientationText = (TextView) findViewById(R.id.orientation);
    }

    protected void initSensor() {
        sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
    }

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

    @Override
    public void onSensorChanged(SensorEvent event) {

        switch (event.sensor.getType()) {
            case Sensor.TYPE_MAGNETIC_FIELD:
                magneticValues = event.values.clone();
                break;
            case Sensor.TYPE_ACCELEROMETER:
                accelerometerValues = event.values.clone();
                break;
        }

        if (magneticValues != null && accelerometerValues != null) {

            SensorManager.getRotationMatrix(inR, I, accelerometerValues, magneticValues);

            SensorManager.remapCoordinateSystem(inR, SensorManager.AXIS_X, SensorManager.AXIS_Z, outR);
            SensorManager.getOrientation(outR, orientationValues);

            int azimuth = (int) (orientationValues[0] * RAD2DEG);
            int pitch = (int) (orientationValues[1] * RAD2DEG);
            int roll = (int) (orientationValues[2] * RAD2DEG);

            // 以下、縦横判定処理
            int absRoll = Math.abs(roll);
            if (mPreOrientation == -1) {
                mPreOrientation = absRoll < VERTICAL_TO_HORIZONTAL_DEGREE ?
                        ORIENTATION_VERTICAL : ORIENTATION_HORIZONTAL;
            } else if (absRoll < 90) {
                mPreOrientation = getOrientation(mPreOrientation, roll);
            } else {
                // プラマイ90度を超える場合は90度未満に置き換えて向きを反転させる。
                int plusMinus = roll >= 0 ? 1 : -1;
                roll = (absRoll - 90) * plusMinus;
                int preOrientation = invertOrientation(mPreOrientation);
                mPreOrientation = invertOrientation(getOrientation(preOrientation, roll));
            }

            // 表示の更新
            azimuthText.setText(String.valueOf(azimuth));
            pitchText.setText(String.valueOf(pitch));
            rollText.setText(String.valueOf(roll));
            orientationText.setText(mPreOrientation == ORIENTATION_VERTICAL ? "縦" : "横");
        }

    }

    /**
     * 与えられた端末の向きを反転させます。
     *
     * @param orientation 端末の向き({@link #ORIENTATION_HORIZONTAL} or {@link #ORIENTATION_VERTICAL} or -1)
     * @return 反転した端末の向き（{@link #ORIENTATION_HORIZONTAL} or {@link #ORIENTATION_VERTICAL} or -1）
     */
    private int invertOrientation(int orientation) {
        if (orientation == ORIENTATION_HORIZONTAL) {
            return ORIENTATION_VERTICAL;
        } else if (orientation == ORIENTATION_VERTICAL) {
            return ORIENTATION_HORIZONTAL;
        } else {
            return -1;
        }
    }

    /**
     * 一つ前の端末の向きと現在の傾きを元に、現在の端末の向きを求めます
     *
     * @param preOrientation 一つ前の端末の向き({@link #ORIENTATION_HORIZONTAL} or {@link #ORIENTATION_VERTICAL} or -1)
     * @param roll           傾き(90度未満)
     * @return 現在の端末の向き（{@link #ORIENTATION_HORIZONTAL} or {@link #ORIENTATION_VERTICAL} or -1）
     */
    private int getOrientation(int preOrientation, int roll) {
        int absRoll = Math.abs(roll);
        if (preOrientation == ORIENTATION_VERTICAL) {
            return (absRoll < VERTICAL_TO_HORIZONTAL_DEGREE) ?
                    ORIENTATION_VERTICAL : ORIENTATION_HORIZONTAL;
        } else if (preOrientation == ORIENTATION_HORIZONTAL) {
            return (absRoll < HORIZONTAL_TO_VERTICAL_DEGREE) ?
                    ORIENTATION_VERTICAL : ORIENTATION_HORIZONTAL;
        } else {
            return -1;
        }
    }
}