Sensor.getRotationMatrix (float[] R, float[] I, float[] gravity, float[] geomagnetic)

public class MainActivity extends AppCompatActivity implements SensorEventListener {  private static final String TAG = "CompassActivity";  private SensorManager sensorManager;  //記錄rotationMatrix矩陣值  private float[] r = new float[9];  private float[] gravity = null;  private float[] geomagnetic = null;  private float[] I=new float[9];  private Handler handler=new Handler(){    @Override    public void handleMessage(Message msg) {      if(gravity!=null&&geomagnetic!=null)      {        if(SensorManager.getRotationMatrix(r, I, gravity, geomagnetic)) {          float gri = gravity[0] * r[6] + gravity[1] * r[7] + gravity[2] * r[8];          float h= (I[3]*r[0]+I[4]*r[3]+I[5]*r[6])*geomagnetic[0]+              (I[3]*r[1]+I[4]*r[4]+I[5]*r[7])*geomagnetic[1]+              (I[3]*r[2]+I[4]*r[5]+I[5]*r[8])*geomagnetic[2];          TextView textView = (TextView) findViewById(R.id.textView);          textView.setText("重力加速度" + gri + "/n"+"磁場強度" + h + "/n");        }      }    }  };  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);  }  @Override  public boolean onCreateOptionsMenu(Menu menu) {    // Inflate the menu; this adds items to the action bar if it is present.    getMenuInflater().inflate(R.menu.menu_main, menu);    return true;  }  @Override  public boolean onOptionsItemSelected(MenuItem item) {    // Handle action bar item clicks here. The action bar will    // automatically handle clicks on the Home/Up button, so long    // as you specify a parent activity in AndroidManifest.xml.    int id = item.getItemId();    //noinspection SimplifiableIfStatement    if (id == R.id.action_settings) {      return true;    }    return super.onOptionsItemSelected(item);  }  @Override  public void onSensorChanged(SensorEvent sensorEvent) {    switch (sensorEvent.sensor.getType()){      case Sensor.TYPE_ACCELEROMETER:        gravity=sensorEvent.values;        handler.sendEmptyMessage(0);        break;      case Sensor.TYPE_MAGNETIC_FIELD:        geomagnetic=sensorEvent.values;        handler.sendEmptyMessage(0);        break;      default:break;    }  }  @Override  public void onAccuracyChanged(Sensor sensor, int i) {  }  private void showMessage(String message){    View view=findViewById(R.id.fab);    final Snackbar snackbar=Snackbar.make(view, message, Snackbar.LENGTH_INDEFINITE);    snackbar.setAction("關閉", new View.OnClickListener() {      @Override      public void onClick(View view) {        snackbar.dismiss();      }    });    snackbar.show();  }  @Override  protected void onPause() {    super.onPause();    sensorManager.unregisterListener(this);  }  @Override  protected void onResume() {    super.onResume();    Sensor sensor1=sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);    sensorManager.registerListener(this,sensor1,SensorManager.SENSOR_DELAY_UI);    Sensor sensor2=sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);    sensorManager.registerListener(this,sensor2,SensorManager.SENSOR_DELAY_UI);  }}