Java tutorial
/* * PhoneGap is available under *either* the terms of the modified BSD license *or* the * MIT License (2008). See http://opensource.org/licenses/alphabetical for full text. * * Copyright (c) 2005-2010, Nitobi Software Inc. * Copyright (c) 2010, IBM Corporation */ package com.phonegap; import java.util.List; import org.json.JSONArray; import org.json.JSONException; import com.phonegap.api.PhonegapActivity; import com.phonegap.api.Plugin; import com.phonegap.api.PluginResult; import android.hardware.Sensor; import android.hardware.SensorEvent; import android.hardware.SensorEventListener; import android.hardware.SensorManager; import android.content.Context; /** * This class listens to the compass sensor and stores the latest heading value. */ public class CompassListener extends Plugin implements SensorEventListener { public static int STOPPED = 0; public static int STARTING = 1; public static int RUNNING = 2; public static int ERROR_FAILED_TO_START = 3; public long TIMEOUT = 30000; // Timeout in msec to shut off listener int status; // status of listener float heading; // most recent heading value long timeStamp; // time of most recent value long lastAccessTime; // time the value was last retrieved private SensorManager sensorManager;// Sensor manager Sensor mSensor; // Compass sensor returned by sensor manager /** * Constructor. */ public CompassListener() { this.timeStamp = 0; this.setStatus(CompassListener.STOPPED); } /** * Sets the context of the Command. This can then be used to do things like * get file paths associated with the Activity. * * @param ctx The context of the main Activity. */ public void setContext(PhonegapActivity ctx) { super.setContext(ctx); this.sensorManager = (SensorManager) ctx.getSystemService(Context.SENSOR_SERVICE); } /** * Executes the request and returns PluginResult. * * @param action The action to execute. * @param args JSONArry of arguments for the plugin. * @param callbackId The callback id used when calling back into JavaScript. * @return A PluginResult object with a status and message. */ public PluginResult execute(String action, JSONArray args, String callbackId) { PluginResult.Status status = PluginResult.Status.OK; String result = ""; try { if (action.equals("start")) { this.start(); } else if (action.equals("stop")) { this.stop(); } else if (action.equals("getStatus")) { int i = this.getStatus(); return new PluginResult(status, i); } else if (action.equals("getHeading")) { // If not running, then this is an async call, so don't worry about waiting if (this.status != RUNNING) { int r = this.start(); if (r == ERROR_FAILED_TO_START) { return new PluginResult(PluginResult.Status.IO_EXCEPTION, ERROR_FAILED_TO_START); } // Wait until running long timeout = 2000; while ((this.status == STARTING) && (timeout > 0)) { timeout = timeout - 100; try { Thread.sleep(100); } catch (InterruptedException e) { e.printStackTrace(); } } if (timeout == 0) { return new PluginResult(PluginResult.Status.IO_EXCEPTION, AccelListener.ERROR_FAILED_TO_START); } } float f = this.getHeading(); return new PluginResult(status, f); } else if (action.equals("setTimeout")) { this.setTimeout(args.getLong(0)); } else if (action.equals("getTimeout")) { long l = this.getTimeout(); return new PluginResult(status, l); } return new PluginResult(status, result); } catch (JSONException e) { e.printStackTrace(); return new PluginResult(PluginResult.Status.JSON_EXCEPTION); } } /** * Identifies if action to be executed returns a value and should be run synchronously. * * @param action The action to execute * @return T=returns value */ public boolean isSynch(String action) { if (action.equals("getStatus")) { return true; } else if (action.equals("getHeading")) { // Can only return value if RUNNING if (this.status == RUNNING) { return true; } } else if (action.equals("getTimeout")) { return true; } return false; } /** * Called when listener is to be shut down and object is being destroyed. */ public void onDestroy() { this.stop(); } //-------------------------------------------------------------------------- // LOCAL METHODS //-------------------------------------------------------------------------- /** * Start listening for compass sensor. * * @return status of listener */ public int start() { // If already starting or running, then just return if ((this.status == CompassListener.RUNNING) || (this.status == CompassListener.STARTING)) { return this.status; } // Get accelerometer from sensor manager List<Sensor> list = this.sensorManager.getSensorList(Sensor.TYPE_ORIENTATION); // If found, then register as listener if (list.size() > 0) { this.mSensor = list.get(0); this.sensorManager.registerListener(this, this.mSensor, SensorManager.SENSOR_DELAY_NORMAL); this.lastAccessTime = System.currentTimeMillis(); this.setStatus(CompassListener.STARTING); } // If error, then set status to error else { this.setStatus(CompassListener.ERROR_FAILED_TO_START); } return this.status; } /** * Stop listening to compass sensor. */ public void stop() { if (this.status != CompassListener.STOPPED) { this.sensorManager.unregisterListener(this); } this.setStatus(CompassListener.STOPPED); } public void onAccuracyChanged(Sensor sensor, int accuracy) { // TODO Auto-generated method stub } /** * Sensor listener event. * * @param SensorEvent event */ public void onSensorChanged(SensorEvent event) { // We only care about the orientation as far as it refers to Magnetic North float heading = event.values[0]; // Save heading this.timeStamp = System.currentTimeMillis(); this.heading = heading; this.setStatus(CompassListener.RUNNING); // If heading hasn't been read for TIMEOUT time, then turn off compass sensor to save power if ((this.timeStamp - this.lastAccessTime) > this.TIMEOUT) { this.stop(); } } /** * Get status of compass sensor. * * @return status */ public int getStatus() { return this.status; } /** * Get the most recent compass heading. * * @return heading */ public float getHeading() { this.lastAccessTime = System.currentTimeMillis(); return this.heading; } /** * Set the timeout to turn off compass sensor if getHeading() hasn't been called. * * @param timeout Timeout in msec. */ public void setTimeout(long timeout) { this.TIMEOUT = timeout; } /** * Get the timeout to turn off compass sensor if getHeading() hasn't been called. * * @return timeout in msec */ public long getTimeout() { return this.TIMEOUT; } /** * Set the status and send it to JavaScript. * @param status */ private void setStatus(int status) { this.status = status; } }