Java tutorial
// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file // for details. All rights reserved. Use of this source code is governed by a // BSD-style license that can be found in the LICENSE file. package com.android.plugins; import java.util.List; import org.apache.cordova.CordovaWebView; import org.apache.cordova.CallbackContext; import org.apache.cordova.CordovaInterface; import org.apache.cordova.CordovaPlugin; import org.apache.cordova.PluginResult; import org.json.JSONArray; import org.json.JSONException; import org.json.JSONObject; import android.content.Context; import android.hardware.Sensor; import android.hardware.SensorEvent; import android.hardware.SensorEventListener; import android.hardware.SensorManager; import android.os.Handler; import android.os.Looper; /** * This class listens to the magnetometer sensor and stores the latest * speed value. */ public class MagnetometerListener extends CordovaPlugin 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; private float x, y, z; // most recent speed values private long timestamp; // time of most recent value private int status; // status of listener private SensorManager sensorManager; // Sensor manager private Sensor mSensor; // Orientation sensor returned by sensor manager private CallbackContext callbackContext; // Keeps track of the JS callback context. private Handler mainHandler = null; private Runnable mainRunnable = new Runnable() { public void run() { MagnetometerListener.this.timeout(); } }; /** * Create an magnetometer listener. */ public MagnetometerListener() { this.x = 0; this.y = 0; this.z = 0; this.timestamp = 0; this.setStatus(MagnetometerListener.STOPPED); } /** * Sets the context of the Command. This can then be used to do things like * get file paths associated with the Activity. * * @param cordova The context of the main Activity. * @param webView The associated CordovaWebView. */ @Override public void initialize(CordovaInterface cordova, CordovaWebView webView) { super.initialize(cordova, webView); this.sensorManager = (SensorManager) cordova.getActivity().getSystemService(Context.SENSOR_SERVICE); } /** * Executes the request. * * @param action The action to execute. * @param args The exec() arguments. * @param callbackId The callback id used when calling back into JavaScript. * @return Whether the action was valid. */ public boolean execute(String action, JSONArray args, CallbackContext callbackContext) { if (action.equals("start")) { this.callbackContext = callbackContext; if (this.status != MagnetometerListener.RUNNING) { // If not running, then this is an async call, so don't worry about waiting // We drop the callback onto our stack, call start, and let start and the sensor callback fire off the callback down the road this.start(); } } else if (action.equals("stop")) { if (this.status == MagnetometerListener.RUNNING) { this.stop(); } } else { // Unsupported action return false; } PluginResult result = new PluginResult(PluginResult.Status.NO_RESULT, ""); result.setKeepCallback(true); callbackContext.sendPluginResult(result); return true; } /** * Called by magnetometer when listener is to be shut down. * Stop listener. */ public void onDestroy() { this.stop(); } //-------------------------------------------------------------------------- // LOCAL METHODS //-------------------------------------------------------------------------- // /** * Start listening for speed sensor. * * @return status of listener */ private int start() { // If already starting or running, then just return if ((this.status == MagnetometerListener.RUNNING) || (this.status == MagnetometerListener.STARTING)) { return this.status; } this.setStatus(MagnetometerListener.STARTING); // Get magnetometer from sensor manager List<Sensor> list = this.sensorManager.getSensorList(Sensor.TYPE_MAGNETIC_FIELD); // If found, then register as listener if ((list != null) && (list.size() > 0)) { this.mSensor = list.get(0); this.sensorManager.registerListener(this, this.mSensor, SensorManager.SENSOR_DELAY_UI); this.setStatus(MagnetometerListener.STARTING); } else { this.setStatus(MagnetometerListener.ERROR_FAILED_TO_START); this.fail(MagnetometerListener.ERROR_FAILED_TO_START, "No sensors found to register magnetometer listening to."); return this.status; } // Set a timeout callback on the main thread. stopTimeout(); mainHandler = new Handler(Looper.getMainLooper()); mainHandler.postDelayed(mainRunnable, 2000); return this.status; } private void stopTimeout() { if (mainHandler != null) { mainHandler.removeCallbacks(mainRunnable); } } /** * Stop listening to magnetometer sensor. */ private void stop() { stopTimeout(); if (this.status != MagnetometerListener.STOPPED) { this.sensorManager.unregisterListener(this); } this.setStatus(MagnetometerListener.STOPPED); } /** * Returns an error if the sensor hasn't started. * * Called two seconds after starting the listener. */ private void timeout() { if (this.status == MagnetometerListener.STARTING) { this.setStatus(MagnetometerListener.ERROR_FAILED_TO_START); this.fail(MagnetometerListener.ERROR_FAILED_TO_START, "Magnetometer could not be started."); } } /** * Called when the accuracy of the sensor has changed. * * @param sensor * @param accuracy */ public void onAccuracyChanged(Sensor sensor, int accuracy) { // DO NOTHING } /** * Sensor listener event. * * @param SensorEvent event */ public void onSensorChanged(SensorEvent event) { // Only look at magnetometer events if (event.sensor.getType() != Sensor.TYPE_MAGNETIC_FIELD) { return; } // If not running, then just return if (this.status == MagnetometerListener.STOPPED) { return; } this.setStatus(MagnetometerListener.RUNNING); // Save time that event was received this.timestamp = System.currentTimeMillis(); this.x = event.values[0]; this.y = event.values[1]; this.z = event.values[2]; this.win(); } /** * Called when the view navigates. */ @Override public void onReset() { if (this.status == MagnetometerListener.RUNNING) { this.stop(); } } @Override public void onResume(boolean multitasking) { if (this.status == MagnetometerListener.STOPPED) { this.start(); } } @Override public void onPause(boolean multitasking) { if (this.status == MagnetometerListener.RUNNING) { this.stop(); } } // Sends an error back to JS private void fail(int code, String message) { // Error object JSONObject errorObj = new JSONObject(); try { errorObj.put("code", code); errorObj.put("message", message); } catch (JSONException e) { e.printStackTrace(); } PluginResult err = new PluginResult(PluginResult.Status.ERROR, errorObj); err.setKeepCallback(true); callbackContext.sendPluginResult(err); } private void win() { // Success return object PluginResult result = new PluginResult(PluginResult.Status.OK, this.getOrientationJSON()); result.setKeepCallback(true); callbackContext.sendPluginResult(result); } private void setStatus(int status) { this.status = status; } private JSONObject getOrientationJSON() { JSONObject r = new JSONObject(); try { r.put("x", this.x); r.put("y", this.y); r.put("z", this.z); r.put("timestamp", this.timestamp); } catch (JSONException e) { e.printStackTrace(); } return r; } }