Android studio button not doing anything really confused

Question

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/background_dark"
    tools:context="com.karanvir.stepcounter.MainActivity">

    <TextView
        android:id="@+id/value"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:textColor="@android:color/holo_orange_light"
        android:textSize="50sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintHorizontal_bias="0.461"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.433"
        tools:layout_constraintBottom_creator="1"
        tools:layout_constraintLeft_creator="1"
        tools:layout_constraintRight_creator="1"
        tools:layout_constraintTop_creator="1" />

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="65dp"
        android:background="@color/colorPrimary"
        app:srcCompat="@drawable/i"
        tools:layout_constraintLeft_creator="1"
        tools:layout_constraintTop_creator="1"
        android:layout_marginTop="66dp"
        app:layout_constraintTop_toBottomOf="@+id/value"
        app:layout_constraintLeft_toLeftOf="parent"
        android:layout_marginLeft="65dp" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="48dp"
        android:background="@android:color/holo_orange_light"
        android:text="How it works"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:ignore="HardcodedText"
        tools:layout_constraintLeft_creator="1"
        tools:layout_constraintRight_creator="1"
        tools:layout_constraintTop_creator="1" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        tools:layout_constraintTop_creator="1"
        tools:layout_constraintLeft_creator="1"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent" />


</android.support.constraint.ConstraintLayout>

package com.karanvir.stepcounter;

import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.util.Locale;



public class MainActivity extends AppCompatActivity implements SensorEventListener{
    private TextView value;
    private SensorManager sensorManager;
    public static DecimalFormat DECIMAL_FORMATTER;
    private SensorManager mSensorManager;
    Button button22;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button22=(Button) findViewById(R.id.button);
        button22.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                openActivity3();
            }
        });






        mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);

        if (mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD) != null){
            //
            Toast.makeText(this, "Success! There's a magnetometer.", Toast.LENGTH_SHORT).show();

        }

        else {
            // Failure! No magnetometer.

openActivity2();



        }

        setContentView(R.layout.activity_main);
        value = (TextView) findViewById(R.id.value);
        // define decimal formatter
        DecimalFormatSymbols symbols = new DecimalFormatSymbols(Locale.US);
        symbols.setDecimalSeparator('.');
        DECIMAL_FORMATTER = new DecimalFormat("#.000", symbols);
        sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
    }



    @Override
    protected void onResume() {
        super.onResume();
        sensorManager.registerListener(this,
                sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD),
                SensorManager.SENSOR_DELAY_NORMAL);
    }
    @Override
    protected void onPause() {
        super.onPause();
        sensorManager.unregisterListener(this);
    }
    @Override
    public void onSensorChanged(SensorEvent event) {
        if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
            // get values for each axes X,Y,Z
            float magX = event.values[0];
            float magY = event.values[1];
            float magZ = event.values[2];
            double magnitude = Math.sqrt((magX * magX) + (magY * magY) + (magZ * magZ));
            // set value on the screen
            value.setText(DECIMAL_FORMATTER.format(magnitude) + " \u00B5");
        }
    }
    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {
    }
    public void openActivity2(){
        Intent intent=new Intent(this, Main2Activity.class);
        startActivity(intent);
    }

    public void openActivity3(){
        Intent intent=new Intent(this, Main3Activity.class);
        startActivity(intent);
    }





}

I have posted all the code for my project, this includes the xml and java code. im learning and just playing around with a project for fun. I have never ran into this error, I think it may have something to do with "public class MainActivity extends AppCompatActivity implements SensorEventListener" as this is my first time using something like this.

Answer 1

You use setContentView(R.layout.activity_main) two times, Remove the second one.

Answer 2

You are setting contentView 2 times.

setContentView(R.layout.activity_main);

Remove the later one.