Moving an image using Accelerometer of android

Question

I have read articles/tutorial about accessing the phone's accelerometer (acceleration and orientation) values. I am trying to build a simple app where I can move a ball image using the these values. Here is my code:

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class Accelerometer extends Activity implements SensorEventListener {
    /** Called when the activity is first created. */
     CustomDrawableView mCustomDrawableView = null; 
     ShapeDrawable mDrawable = new ShapeDrawable(); 
      int x ; 
       int y ;

    private SensorManager sensorManager = null;

       /** Called when the activity is first created. */
       @Override
       public void onCreate(Bundle savedInstanceState) {

           super.onCreate(savedInstanceState);
           // Get a reference to a SensorManager
           sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
           mCustomDrawableView = new CustomDrawableView(this); 
           setContentView(mCustomDrawableView); 
         //  setContentView(R.layout.main);

       }

       // This method will update the UI on new sensor events
       public void onSensorChanged(SensorEvent sensorEvent) {
         {
         if (sensorEvent.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {

         int someNumber = 100;
         float xChange = someNumber * sensorEvent.values[1];
         //values[2] can be -90 to 90
         float yChange = someNumber * 2 * sensorEvent.values[2];       
             x = x + (int)xChange;
             y = y + (int)yChange;

         }


         if (sensorEvent.sensor.getType() == Sensor.TYPE_ORIENTATION) {

         }
        }
       }

       // I've chosen to not implement this method
       public void onAccuracyChanged(Sensor arg0, int arg1) {
     // TODO Auto-generated method stub

    }

       @Override
       protected void onResume() {
        super.onResume();
        // Register this class as a listener for the accelerometer sensor
        sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_NORMAL);
        // ...and the orientation sensor
        sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION), SensorManager.SENSOR_DELAY_NORMAL);
       }

       @Override
       protected void onStop() {
        // Unregister the listener
        sensorManager.unregisterListener(this);
        super.onStop();
       } 
       public  class CustomDrawableView extends View { 

           public CustomDrawableView(Context context) { 
               super(context); 

               int width = 50; 
               int height = 50; 
               mDrawable = new ShapeDrawable(new OvalShape()); 
               mDrawable.getPaint().setColor(0xff74AC23); 
               mDrawable.setBounds(x, y, x + width, y + height); 
           } 
           protected void onDraw(Canvas canvas) { 
               mDrawable.draw(canvas); 
               invalidate(); 
           } 
       }
}

I am getting an oval shape displayed on the screen but nothing happens after that.

thanks

Answer 1

Use this code. You were never setting the location of the drawable after you intialized that class. You'll have to do some calculations to set the balls location properly. The way you were doing it was getting values over 10000 which was drawing the oval off screen.

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.View;

public class Accelerometer extends Activity implements SensorEventListener
{
    /** Called when the activity is first created. */
    CustomDrawableView mCustomDrawableView = null;
    ShapeDrawable mDrawable = new ShapeDrawable();
    public static int x;
    public static int y;

    private SensorManager sensorManager = null;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {

        super.onCreate(savedInstanceState);
        // Get a reference to a SensorManager
        sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
        mCustomDrawableView = new CustomDrawableView(this);
        setContentView(mCustomDrawableView);
        // setContentView(R.layout.main);

    }

    // This method will update the UI on new sensor events
    public void onSensorChanged(SensorEvent sensorEvent)
    {
        {
            if (sensorEvent.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
                // the values you were calculating originally here were over 10000!
                x = (int) Math.pow(sensorEvent.values[1], 2); 
                y = (int) Math.pow(sensorEvent.values[2], 2);

            }

            if (sensorEvent.sensor.getType() == Sensor.TYPE_ORIENTATION) {

            }
        }
    }

    // I've chosen to not implement this method
    public void onAccuracyChanged(Sensor arg0, int arg1)
    {
        // TODO Auto-generated method stub

    }

    @Override
    protected void onResume()
    {
        super.onResume();
        // Register this class as a listener for the accelerometer sensor
        sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
                SensorManager.SENSOR_DELAY_NORMAL);
        // ...and the orientation sensor
        sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION),
                SensorManager.SENSOR_DELAY_NORMAL);
    }

    @Override
    protected void onStop()
    {
        // Unregister the listener
        sensorManager.unregisterListener(this);
        super.onStop();
    }

    public class CustomDrawableView extends View
    {
        static final int width = 50;
        static final int height = 50;

        public CustomDrawableView(Context context)
        {
            super(context);

            mDrawable = new ShapeDrawable(new OvalShape());
            mDrawable.getPaint().setColor(0xff74AC23);
            mDrawable.setBounds(x, y, x + width, y + height);
        }

        protected void onDraw(Canvas canvas)
        {
            RectF oval = new RectF(Accelerometer.x, Accelerometer.y, Accelerometer.x + width, Accelerometer.y
                    + height); // set bounds of rectangle
            Paint p = new Paint(); // set some paint options
            p.setColor(Color.BLUE);
            canvas.drawOval(oval, p);
            invalidate();
        }
    }
}

Answer 2

Here is my implementation of this problem. Dymmeh's solution kept throwing problems at me, so I refactored it until I got it working.

package edu.ian495.accelerometertest;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.Menu;
import android.widget.ImageView;

public class MainActivity extends Activity implements SensorEventListener {
    private SensorManager sensorManager;
    private Sensor accelerometer;
    private long lastUpdate;

    AnimatedView animatedView = null;
    ShapeDrawable mDrawable = new ShapeDrawable();
    public static int x;
    public static int y;

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

        sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
        accelerometer = sensorManager
                .getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        lastUpdate = System.currentTimeMillis();

        animatedView = new AnimatedView(this);
        setContentView(animatedView);
    }

    @Override
    protected void onResume() {
        super.onResume();
        sensorManager.registerListener(this, accelerometer,
                SensorManager.SENSOR_DELAY_GAME);
    }

    @Override
    protected void onPause() {
        super.onPause();
        sensorManager.unregisterListener(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    @Override
    public void onAccuracyChanged(Sensor arg0, int arg1) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onSensorChanged(SensorEvent event) {
        // TODO Auto-generated method stub
        if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {

            x -= (int) event.values[0];
            y += (int) event.values[1];

        }
    }

    public class AnimatedView extends ImageView {

        static final int width = 50;
        static final int height = 50;

        public AnimatedView(Context context) {
            super(context);
            // TODO Auto-generated constructor stub

            mDrawable = new ShapeDrawable(new OvalShape());
            mDrawable.getPaint().setColor(0xffffAC23);
            mDrawable.setBounds(x, y, x + width, y + height);

        }

        @Override
        protected void onDraw(Canvas canvas) {

            mDrawable.setBounds(x, y, x + width, y + height);
            mDrawable.draw(canvas);
            invalidate();
        }
    }

}

Answer 3

I have done some changes in onSensorChange code to move the ball in the screen. With the example in my case the ball don´t move correctly and for that I did the changes. This example Works fine for my.

public void onSensorChanged(SensorEvent sensorEvent)
{
    //Try synchronize the events
    synchronized(this){
    //For each sensor
    switch (sensorEvent.sensor.getType()) {
    case Sensor.TYPE_MAGNETIC_FIELD: //Magnetic sensor to know when the screen is landscape or portrait
        //Save values to calculate the orientation
        mMagneticValues = sensorEvent.values.clone();
        break;
    case Sensor.TYPE_ACCELEROMETER://Accelerometer to move the ball
        if (bOrientacion==true){//Landscape
            //Positive values to move on x
            if (sensorEvent.values[1]>0){
                //In margenMax I save the margin of the screen this value depends of the screen where we run the application. With this the ball not disapears of the screen
                if (x<=margenMaxX){
                    //We plus in x to move the ball
                    x = x + (int) Math.pow(sensorEvent.values[1], 2);
                }
            }
            else{
                //Move the ball to the other side
                if (x>=margenMinX){
                    x = x - (int) Math.pow(sensorEvent.values[1], 2);
                }
            }
            //Same in y
            if (sensorEvent.values[0]>0){
                if (y<=margenMaxY){
                    y = y + (int) Math.pow(sensorEvent.values[0], 2);
                }
            }
            else{
                if (y>=margenMinY){
                    y = y - (int) Math.pow(sensorEvent.values[0], 2);
                }
            }
        }
        else{//Portrait
            //Eje X
            if (sensorEvent.values[0]<0){
                if (x<=margenMaxX){
                    x = x + (int) Math.pow(sensorEvent.values[0], 2);
                }
            }
            else{
                if (x>=margenMinX){
                    x = x - (int) Math.pow(sensorEvent.values[0], 2);
                }
            }
            //Eje Y
            if (sensorEvent.values[1]>0){
                if (y<=margenMaxY){
                    y = y + (int) Math.pow(sensorEvent.values[1], 2);
                }
            }
            else{
                if (y>=margenMinY){
                    y = y - (int) Math.pow(sensorEvent.values[1], 2);
                }
            }

        }
        //Save the values to calculate the orientation
        mAccelerometerValues = sensorEvent.values.clone();
        break;  
    case Sensor.TYPE_ROTATION_VECTOR:  //Rotation sensor
        //With this value I do the ball bigger or smaller
        if (sensorEvent.values[1]>0){
            z=z+ (int) Math.pow(sensorEvent.values[1]+1, 2);
        }
        else{
            z=z- (int) Math.pow(sensorEvent.values[1]+1, 2);                    
        }

    default:
        break;
    }
    //Screen Orientation
    if (mMagneticValues != null && mAccelerometerValues != null) {
        float[] R = new float[16];
        SensorManager.getRotationMatrix(R, null, mAccelerometerValues, mMagneticValues);
        float[] orientation = new float[3];
        SensorManager.getOrientation(R, orientation);
        //if x have positives values the screen orientation is landscape in other case is portrait
        if (orientation[0]>0){//LandScape
            //Here I change the margins of the screen for the ball not disapear
            bOrientacion=true;
            margenMaxX=1200;
            margenMinX=0;
            margenMaxY=500;
            margenMinY=0;
        }
        else{//Portrait
            bOrientacion=false;
            margenMaxX=600;
            margenMinX=0;
            margenMaxY=1000;
            margenMinY=0;
        }

    }
    }
}

The view class where I draw the ball

public class CustomDrawableView extends View
{
    static final int width = 50;
    static final int height = 50;
    //Constructor de la figura
    public CustomDrawableView(Context context)
    {
        super(context);

        mDrawable = new ShapeDrawable(new OvalShape());
        mDrawable.getPaint().setColor(0xff74AC23);
        mDrawable.setBounds(x, y, x + width, y + height);
    }
    //Dibujamos la figura
    protected void onDraw(Canvas canvas)
    {
        //Actividad_Principal x,y,z are variables from the main activity where I have the onSensorChange
        RectF oval = new RectF(Actividad_Principal.x+Actividad_Principal.z, Actividad_Principal.y+Actividad_Principal.z, Actividad_Principal.x + width, Actividad_Principal.y + height);             
        Paint p = new Paint(); 
        p.setColor(Color.BLUE);
        canvas.drawOval(oval, p);
        invalidate();
    }
}

}

That is all, I hope help us.