How can I access the gyroscope from onResume?

Question

I have some code that aims to count how many times the user turns too quickly. I implemented a gyroscope and have some code working within on Resume to collect the data, along with some voice outputs. However, I am having problems making the gyroscope work properly within onResume. For one, the voice outputs do not work properly, and goes out of order. Next, I still am not getting values for the gyroscope.

package com.example.shivamgandhi.gyrosafe;

import android.content.Context;
import android.content.Intent;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RelativeLayout;
import android.widget.TextView;

public class Balance_Test_Activity extends VoiceControl implements View.OnClickListener, SensorEventListener, View.OnTouchListener {

    int n = 2;
    Button btnarray[] = new Button[n];
    private SensorManager mSensorManager;
    private Sensor default_gyro;
    private TextView textView79;
    RelativeLayout RelativeLayout;
    int count1 = 0;
    float axisX, axisY, axisZ;
    double omegaMagnitude;
    EditText ed29;
    private static final float NS2S = 1.0f / 1000000000.0f;
    private final float[] deltaRotationVector = new float[4];
    int touch = 0;

    int count2 = 0;
    int time1 = 0;
    int time2 = 0;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.balance_test);

        RelativeLayout = (RelativeLayout)findViewById(R.id.RelativeLayout4);

        btnarray[0] = (Button)findViewById(R.id.button10);
        btnarray[1] = (Button)findViewById(R.id.button20);

        mSensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);
        default_gyro = mSensorManager.getDefaultSensor(Sensor.TYPE_GYROSCOPE);

        textView79 = (TextView)findViewById(R.id.textView79);

        ed29 = (EditText)findViewById(R.id.editText29);

        for(int i = 0; i <n; i++){
            btnarray[i].setOnClickListener(this);
        }

        RelativeLayout.setOnTouchListener(this);

    }

    //when this Activity starts
    @Override
    protected void onResume()
    {
        super.onResume();

        if (touch == 1){
            try{
                speakWords("Please place your hands on your hips and keep your feet under your shoulders. Hold your balance for the next 20 seconds");
                Thread.sleep(2000);
                while(time1 < 334){
                    mSensorManager.registerListener(this, default_gyro, SensorManager.SENSOR_DELAY_UI);
                    if(omegaMagnitude > 2){
                        count1 ++;
                        time1 ++;
                    }
                    else{
                        time1 ++;
                    }
                }
                Thread.sleep(2000);
                speakWords("Place your hands by your side. Tap to continue.");
                Thread.sleep(1000);
                touch = 10;
            }
            catch(InterruptedException e){
                e.printStackTrace();
            }
        }

        if (touch == 2){
            speakWords("Please place your hands on your hips and stand on your nondominant foot for the next 20 seconds");
            while(time2 < 334){
                mSensorManager.registerListener(this, default_gyro, SensorManager.SENSOR_DELAY_UI);
                if(omegaMagnitude > 2){
                    count2 ++;
                    time1 ++;
                }
                else{
                    time1 ++;
                }
            }
            speakWords("You may resume normal stance now");
            touch = 20;
        }


    }

    @Override
    protected void onStop()
    {
        //unregister the sensor listener
        mSensorManager.unregisterListener(this);
        super.onStop();
    }

    @Override
    public void onClick(View v){
        if(v == findViewById(R.id.button10)){
            Intent myIntent = new Intent(this, Results_Page_Activity.class);
            startActivity(myIntent);
        }
    }

    @Override
    public boolean onTouch(View v, MotionEvent event){
        if(v == RelativeLayout){
           if(touch == 0){
               touch = 1;
               onResume();
               return true;
           }
            else if (touch == 10){
               touch = 2;
               onResume();
               return true;
           }
            return true;
        }
        else{
            return false;
        }
    }

    @Override
    public void onAccuracyChanged(Sensor arg0, int arg1)
    {
        //Do nothing.
    }


    public void onSensorChanged(SensorEvent event) {
        // This timestep's delta rotation to be multiplied by the current rotation
        // after computing it from the gyro sample data.

        // Axis of the rotation sample, not normalized yet.
        float axisX = event.values[0];
        float axisY = event.values[1];
        float axisZ = event.values[2];

        // Calculate the angular speed of the sample
        double omegaMagnitude = Math.sqrt(axisX*axisX + axisY*axisY + axisZ*axisZ);

        float[] deltaRotationMatrix = new float[9];
        SensorManager.getRotationMatrixFromVector(deltaRotationMatrix, deltaRotationVector);

        textView79.setText("Gyro X (Roll) :" + Float.toString(event.values[2]) + "\n" +
                "Gyro Y (Pitch) :" + Float.toString(event.values[1]) + "\n" +
                "Gyro Z (Yaw) :" + Float.toString(event.values[0]));
    }
}

How do I go about fixing this code so that I can actually retrieve values from the gyroscope? Thanks in advance :)

Answer 1

Ok, several issues here.

1)Never sleep in onResume, or anywhere else on the UI thread. You can't hold it up like that. At best doing so will cause you to look like you've crashed, at worst it will actually crash due to a watchdog. It will almost never do what you want.

2)You're never actually setting imegaMagnitude, because you have it redefined in onSensorChanged

3)You won't see the right value anyway, because it won't be set until onSensorChanged is called. Since that's only called on the UI thread, it won't be called until after onResume finishes (see 1). So your code can never work anyway.

4)You can't call onResume yourself. Only the framework is allowed to call lifecycle functions. Doing so yourself will seriously screw things up.

Your approach is completely unsuable. Rewrite your logic to use event based processing and a state machine pattern. This code isn't salvagable.