안드로이드의 버튼 링크

package fit.korea2canada.com.jjfitv1;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ImageButton;

public class MainActivity extends AppCompatActivity {

    ImageButton WalkingButton;
    ImageButton WorkoutButton;
    ImageButton WeightButton;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        startService(new Intent(this, SensorListener.class));

        setContentView(R.layout.activity_main);

        WalkingButton = (ImageButton) findViewById(R.id.btnWalking);
        WorkoutButton = (ImageButton) findViewById(R.id.btnWorkout);
        WeightButton = (ImageButton) findViewById(R.id.btnWeight);

        WalkingButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getApplicationContext(), StepperActivity.class);
                startActivity(intent);
            }
        });

        WorkoutButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getApplicationContext(), WorkoutActivity.class);
                startActivity(intent);
            }
        });

        WeightButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getApplicationContext(), WeightActivity.class);
                startActivity(intent);
            }
        });
    }


/*
    public void onBtnClick(View v) {
        Thread thread = new Thread(){
            @Override
            public void run() {
                super.run();
                for (int i=0; i<=100;) {
                    try{
                        sleep(1000);
                    } catch (InterruptedException e){
                        e.printStackTrace();
                    }
                    pgBar.setProgress(i);
                    i=i+10;
                }
            }
        };
        thread.start();
    }

*/

}

[Activity_main]

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    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:orientation="vertical"
    android:weightSum="1"
    tools:context="fit.korea2canada.com.jjfitv1.MainActivity">


    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Just Fit"
        android:textAlignment="center"
        android:textSize="50sp"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginBottom="10dp"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp"
        android:layout_marginTop="10dp"
        android:gravity="center_horizontal"
        android:orientation="vertical">


        <ImageButton
            android:id="@+id/btnWalking"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginBottom="10dp"
            android:layout_weight="1"
            android:background="@android:color/background_light"
            android:paddingBottom="0dp"
            android:scaleType="centerCrop"
            app:srcCompat="@drawable/walkinglogo" />

        <ImageButton
            android:id="@+id/btnWorkout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginBottom="15dp"
            android:layout_weight="1"
            android:background="@android:color/background_light"
            android:scaleType="centerCrop"
            app:srcCompat="@drawable/workoutlogo" />

        <ImageButton
            android:id="@+id/btnWeight"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginBottom="5dp"
            android:layout_weight="1"
            android:background="@android:color/background_light"
            android:scaleType="centerCrop"
            app:srcCompat="@drawable/weightlogo" />

    </LinearLayout>

</LinearLayout>