StackOverflow2013

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POAndroid: Using the accelerometer to detect a flick
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copied!<p>I'm trying to develop an app where the user can hit an invisible drum using the motion of the phone. So that when the phone is flicked downwards a drum is sounded at the end of the flick.</p> <p>I have managed to get 90% of this working, by detecting when a large, quick movement suddenly stops. But although the drum is being sounded after a flick (good) it's also being sounded at the end of a pull (not desirable). </p> <p>By flick I mean the phone is being flicked forwards and downwards, as if you are striking a drum with it, and by pull I mean you are returning your arm back to the starting position.</p> <p>Does anyone know an efficient way of determining when a flick occurs but not a push?</p> <p>Any ideas will be gratefully received.</p> <p>Thanks</p> <p>EXISTING CODE:</p> <pre><code>package com.example.testaccelerometer; import android.hardware.Sensor; import android.hardware.SensorEvent; import android.hardware.SensorEventListener; import android.hardware.SensorListener; import android.hardware.SensorManager; import android.os.Bundle; import android.app.Activity; import android.content.Context; import android.view.Menu; import android.widget.TextView; public class MainActivity extends Activity implements SensorEventListener{ public static TextView results; public static TextView clickresults; StringBuilder builder = new StringBuilder(); private float mAccelNoGrav; private float mAccelWithGrav; private float mLastAccelWithGrav; public static boolean shakeIsHappening; public static int beatnumber = 0; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); results = (TextView) findViewById(R.id.results); clickresults = (TextView) findViewById(R.id.clickresults); SensorManager manager = (SensorManager) getSystemService(Context.SENSOR_SERVICE); Sensor accelerometer = manager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); if(!manager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_FASTEST)){ builder.append("Problem with Accelerometer - Shaking will not work"); }; mAccelNoGrav = 0.00f; mAccelWithGrav = SensorManager.GRAVITY_EARTH; mLastAccelWithGrav = SensorManager.GRAVITY_EARTH; } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } @Override public void onAccuracyChanged(Sensor sensor, int accuracy) { // TODO Auto-generated method stub } @Override public void onSensorChanged(SensorEvent event) { builder.setLength(0); builder.append("X " + event.values[0] + "\nY " + event.values[1] + "\nZ " + event.values[2]); results.setText(builder.toString()); float x = event.values[0]; float y = event.values[1]; float z = event.values[2]; mLastAccelWithGrav = mAccelWithGrav; mAccelWithGrav = android.util.FloatMath.sqrt(x*x + y*y + z*z); float delta = mAccelWithGrav - mLastAccelWithGrav; mAccelNoGrav = mAccelNoGrav * 0.9f + delta; if (mAccelNoGrav >8.5) { shakeIsHappening = true; //clickresults.append(" click " + mAccel); } if (shakeIsHappening == true && mAccelNoGrav <2) { beatnumber++; clickresults.append(" click number: " + beatnumber + "\n" + "PA: " + mLastAccelWithGrav + " CA:" + mAccelNoGrav + "\n "); shakeIsHappening = false; } } @Override protected void onResume() { super.onResume(); // YOU DO NEED TO TRY AND REREGISTER IT NOW } @Override protected void onPause() { // YOU DO NEED TO TRY AND UNREGISTER IT NOW super.onPause(); } } </code></pre>

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