Question

im trying to make an speedometer using the accelerometer but for some reason the code is crashing can someone please tell me what is wrong and how to fix it
thank you

this is the red part in logcat:

05-14 13:03:55.826: INFO/ActivityManager(91): Start proc com.hanud.speedo for activity com.hanud.speedo/.speedometer: pid=2052 uid=10127 gids={}
05-14 13:03:56.806: DEBUG/AndroidRuntime(2052): Shutting down VM
05-14 13:03:56.806: WARN/dalvikvm(2052): threadid=1: thread exiting with uncaught exception (group=0x400207f0)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052): FATAL EXCEPTION: main
05-14 13:03:56.986: ERROR/AndroidRuntime(2052): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.hanud.speedo/com.hanud.speedo.speedometer}: java.lang.ClassNotFoundException: com.hanud.speedo.speedometer in loader dalvik.system.PathClassLoader[/data/app/com.hanud.speedo-2.apk]
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at android.os.Looper.loop(Looper.java:123)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at android.app.ActivityThread.main(ActivityThread.java:4627)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at java.lang.reflect.Method.invokeNative(Native Method)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at java.lang.reflect.Method.invoke(Method.java:521)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at dalvik.system.NativeStart.main(Native Method)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052): Caused by: java.lang.ClassNotFoundException: com.hanud.speedo.speedometer in loader dalvik.system.PathClassLoader[/data/app/com.hanud.speedo-2.apk]
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:243)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at java.lang.ClassLoader.loadClass(ClassLoader.java:573)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at java.lang.ClassLoader.loadClass(ClassLoader.java:532)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
05-14 13:03:56.986: ERROR/AndroidRuntime(2052):     ... 11 more
05-14 13:03:57.017: WARN/ActivityManager(91):   Force finishing activity com.hanud.speedo/.speedometer
05-14 13:03:57.526: WARN/ActivityManager(91): Activity pause timeout for HistoryRecord{4382d820 com.hanud.speedo/.speedometer}
05-14 13:04:05.666: DEBUG/dalvikvm(1890): GC_EXPLICIT freed 4544 objects / 322792 bytes in 288ms
05-14 13:04:07.796: WARN/ActivityManager(91): Activity destroy timeout for HistoryRecord{4382d820 com.hanud.speedo/.speedometer}
05-14 13:04:12.016: INFO/ActivityManager(91): Start proc com.android.email for service com.android.email/.service.MailService: pid=2058 uid=10004 gids={3003, 1015}

and this is the code:

import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

import android.app.Activity;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;

public class Speedometer extends Activity {

  Handler handler = new Handler();

  SensorManager sensorManager;
    TextView myTextView;

    float appliedAcceleration = 0;
    float currentAcceleration = 0;
    float velocity = 0;
    Date lastUpdate;    

    @Override
    public void onCreate(Bundle icicle) {
      super.onCreate(icicle);
      setContentView(R.layout.main);

      myTextView = (TextView)findViewById(R.id.myTextView);
      lastUpdate = new Date(System.currentTimeMillis());

      sensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);
      Sensor accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        sensorManager.registerListener(sensorEventListener,
                                       accelerometer,
                                       SensorManager.SENSOR_DELAY_FASTEST);


      Timer updateTimer = new Timer("velocityUpdate");
      updateTimer.scheduleAtFixedRate(new TimerTask() {
        public void run() {
          updateGUI();
        }
      }, 0, 1000);
    }

    private void updateGUI() {
      // Convert from meters per second to miles per hour.
      final double mph = (Math.round(100*velocity / 1.6 * 3.6))/100;

      // Update the GUI
      handler.post(new Runnable() {
      public void run() {
          myTextView.setText(String.valueOf(mph) + "mph");
      }
    });
    }

  private void updateVelocity() {
      // Calculate how long this acceleration has been applied.
      Date timeNow = new Date(System.currentTimeMillis());
      long timeDelta = timeNow.getTime()-lastUpdate.getTime();
      lastUpdate.setTime(timeNow.getTime());

      // Calculate the change in velocity at the 
      // current acceleration since the last update. 
      float deltaVelocity = appliedAcceleration * (timeDelta/1000);
      appliedAcceleration = currentAcceleration;

      // Add the velocity change to the current velocity.
      velocity += deltaVelocity;
    }

  //private final SensorListener sensorListener = new SensorListener() {
  private final SensorEventListener sensorEventListener = new SensorEventListener() {
    double calibration = Double.NaN;



      public void onSensorChanged(SensorEvent event) {
        double x = event.values[0];
        double y = event.values[1];
        double z = event.values[2];

      double a = Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2) + Math.pow(z, 2)); 

      if (calibration == Double.NaN)
        calibration = a;
      else {
        updateVelocity();
        currentAcceleration = (float)a;
      }
    }
      public void onAccuracyChanged(Sensor sensor, int accuracy) { }
  };
}

Answer 1

You defined (probably in the android manifest) com.hanud.speedo.speedometer, while your activity’s name is Speedometer (with capital S).

Just to make it clear – change the name of the activity in the Manifest file to Speedometer.