Android accelerometer plays a beep when x-axis changes

Question

I am new to Android studio i am just using online sources to learn Android. I want to make an app that plays a beeps sound when x-axis of the accelerometer changes.

Here is my code:

package com.hamzah.accelerometer;

import android.content.res.AssetFileDescriptor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import android.media.MediaPlayer;


public class MainActivity extends AppCompatActivity implements 
SensorEventListener {

private float mLastX, mLastY, mLastZ;
private boolean mInitialized;
private SensorManager mSensorManager;
private Sensor mAccelerometer;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mInitialized = false;
    mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
    mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
    mSensorManager.registerListener(this, mAccelerometer , SensorManager.SENSOR_DELAY_NORMAL);
    final MediaPlayer player = MediaPlayer.create(this, R.raw.beep);
}
protected void onResume() {
    super.onResume();
    mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
}
protected void onPause() {
    super.onPause();
    mSensorManager.unregisterListener(this);
}

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

}

@Override
public void onSensorChanged(SensorEvent event){
    TextView tvX= (TextView)findViewById(R.id.x_axis);
    TextView tvY= (TextView)findViewById(R.id.y_axis);
    TextView tvZ= (TextView)findViewById(R.id.z_axis);
    float x = event.values[0];
    float y = event.values[1];
    float z = event.values[2];
    if (!mInitialized) {
        mLastX = x;
        mLastY = y;
        mLastZ = z;
        tvX.setText("0.0");
        tvY.setText("0.0");
        tvZ.setText("0.0");
        mInitialized = true;
    } else {
        float deltaX = Math.abs(mLastX - x);
        float deltaY = Math.abs(mLastY - y);
        float deltaZ = Math.abs(mLastZ - z);
        float NOISE = (float) 2.0;
        if (deltaX < NOISE) deltaX = (float)0.0;
        if (deltaY < NOISE) deltaY = (float)0.0;
        if (deltaZ < NOISE) deltaZ = (float)0.0;
        mLastX = x;
        mLastY = y;
        mLastZ = z;
        tvX.setText(Float.toString(deltaX));
        tvY.setText(Float.toString(deltaY));
        tvZ.setText(Float.toString(deltaZ));
        if (deltaX > deltaY) {
            player.start();
        } else {
            iv.setVisibility(View.INVISIBLE);
        }
    }
}
}

I don't know how to do this what I have done is that if the acceleration in x-axis is more than acceleration in y-axis then a beep should play (which I have uploaded in the raw folder).

There is definitely a problem in player.start(), I don't know how to code this part.

Answer 1

You are trying to cast method "player.start();" inside of the body of onSensorChanged(SensorEvent event). Your object player is declared inside of onCreate(Bundle savedInstanceState). So it can be used only here. You have to declare

private final MediaPlayer player;

and then initialize it in onCreate

player = MediaPlayer.create(this, R.raw.beep);