Android Compass Code Example

Today I'm going to share a working code to make a very simple compass application for your android device. Some android device (like Huawei Y300 and Lenovo P700i) does not have full support of motions sensors so this code will not work for them.

Video Demo

Our code for today will run just like this.

Video Demo Permalink

DOWNLOAD CODE

Files Needed

You need to create your own compass image. For this example, I'm using a stock photo. Your image must be a PNG with transparent background, do not use this jpg file I used.

Let's Code

Here's our MainActivity.java

package com.example.compassapp;

import android.app.Activity;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.animation.Animation;
import android.view.animation.RotateAnimation;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends Activity implements SensorEventListener {

    // define the display assembly compass picture
    private ImageView image;

    // record the compass picture angle turned
    private float currentDegree = 0f;

    // device sensor manager
    private SensorManager mSensorManager;

    TextView tvHeading;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // our compass image 
        image = (ImageView) findViewById(R.id.imageViewCompass);

        // TextView that will tell the user what degree is he heading
        tvHeading = (TextView) findViewById(R.id.tvHeading);

        // initialize your android device sensor capabilities
        mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
    }

    @Override
    protected void onResume() {
        super.onResume();
        
        // for the system's orientation sensor registered listeners
        mSensorManager.registerListener(this, mSensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION),
                SensorManager.SENSOR_DELAY_GAME);
    }

    @Override
    protected void onPause() {
        super.onPause();
        
        // to stop the listener and save battery
        mSensorManager.unregisterListener(this);
    }

    @Override
    public void onSensorChanged(SensorEvent event) {

        // get the angle around the z-axis rotated
        float degree = Math.round(event.values[0]);

        tvHeading.setText("Heading: " + Float.toString(degree) + " degrees");

        // create a rotation animation (reverse turn degree degrees)
        RotateAnimation ra = new RotateAnimation(
                currentDegree, 
                -degree,
                Animation.RELATIVE_TO_SELF, 0.5f, 
                Animation.RELATIVE_TO_SELF,
                0.5f);

        // how long the animation will take place
        ra.setDuration(210);

        // set the animation after the end of the reservation status
        ra.setFillAfter(true);

        // Start the animation
        image.startAnimation(ra);
        currentDegree = -degree;

    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {
        // not in use
    }
}

Our layout file activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#fff" >

    <TextView
        android:id="@+id/tvHeading"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="40dp"
        android:layout_marginTop="20dp"
        android:text="Heading: 0.0" />

    <ImageView
        android:id="@+id/imageViewCompass"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvHeading"
        android:layout_centerHorizontal="true"
        android:src="@drawable/img_compass" />

</RelativeLayout>

Some notes

My app orientation is locked to portrait mode.
There are no special permissions in the Manifest file.

Further Readings

Android SensorManager
Android RotateAnimation
Android Motion Sensors

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