代写mobile platform、代做R、代写programming留学生、代做R编程语言

日期：2019-04-17 10:28

Android Pedometer

1. Purpose

(1) By programming an Android pedometer program using mobile platform,we learn

to familiarize the calling methods of mobile platform sensors.

(2) Simple mobile apps’ design and implementation.

2. Contents

(1) Acceleration sensor’s application

By using a compiler like Eclipse, write an Android program which could realize

the function listed below.

1st? Use the acceleration sensor to measure the mobile’s acceleration in the X,Y

and Z axis directions and the scalar value of the total acceleration.

2nd? Display the results on the screen.

3rd? Record the results in the specified file.

The relative position of the mobile’s X,Y and Z axis derections is showed in the picture below

Reference Code:

package com.practice.cos;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.RandomAccessFile;

import java.text.DecimalFormat;

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.Environment;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.TextView;

public class PracticeActivity extends Activity implements SensorEventListener,

OnClickListener {

/** Called when the activity is first created. */

//Create a LOG label

private Button mWriteButton, mStopButton;

private boolean doWrite = false;

private SensorManager sm;

private float lowX = 0, lowY = 0, lowZ = 0;

private final float FILTERING_VALAUE = 0.1f;

private TextView AT,ACT;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

AT = (TextView)findViewById(R.id.AT);

ACT = (TextView)findViewById(R.id.onAccuracyChanged);

//Create a SensorManager to get the system’s sensor service

sm =

(SensorManager)getSystemService(Context.SENSOR_SERVICE);

/*

*Using the most common method to register an event

* Parameter1 ：SensorEventListener detectophone

* Parameter2 ：Sensor one service could have several Sensor

realizations.Here,We use getDefaultSensor to get the defaulted Sensor

* Parameter3 ：Mode We can choose the refresh frequency of the

data change

* */

// Register the acceleration sensor

sm.registerListener(this,

sm.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),

SensorManager.SENSOR_DELAY_FASTEST);//High

sampling rate；.SENSOR_DELAY_NORMAL means a lower sampling rate

try {

FileOutputStream fout = openFileOutput("acc.txt",

Context.MODE_PRIVATE);

fout.close();

} catch (IOException e) {

e.printStackTrace();

}

mWriteButton = (Button) findViewById(R.id.Button_Write);

mWriteButton.setOnClickListener(this);

mStopButton = (Button) findViewById(R.id.Button_Stop);

mStopButton.setOnClickListener(this);

}

public void onPause(){

super.onPause();

}

public void onClick(View v) {

if (v.getId() == R.id.Button_Write) {

doWrite = true;

}

if (v.getId() == R.id.Button_Stop) {

doWrite = false;

}

}

public void onAccuracyChanged(Sensor sensor, int accuracy) {

ACT.setText("onAccuracyChanged is detonated");

}

public void onSensorChanged(SensorEvent event) {

String message = new String();

if(event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {

float X = event.values[0];

float Y = event.values[1];

float Z = event.values[2];

//Low-Pass Filter

lowX = X * FILTERING_VALAUE + lowX * (1.0f -

FILTERING_VALAUE);

lowY = Y * FILTERING_VALAUE + lowY * (1.0f -

FILTERING_VALAUE);

lowZ = Z * FILTERING_VALAUE + lowZ * (1.0f -

FILTERING_VALAUE);

//High-pass filter

float highX = X - lowX;

float highY = Y - lowY;

float highZ = Z - lowZ;

double highA = Math.sqrt(highX * highX + highY * highY + highZ

* highZ);

DecimalFormat df = new DecimalFormat("#,##0.000");

message = df.format(highX) + " ";

message += df.format(highY) + " ";

message += df.format(highZ) + " ";

message += df.format(highA) + "\n";

AT.setText(message + "\n");

if (doWrite) {

write2file(message);

}

}

}

private void write2file(String a){

try {

File file = new File("/sdcard/acc.txt");//write the result

into/sdcard/acc.txt

if (!file.exists()){

file.createNewFile();}

// Open a random access file stream for reading and writing

RandomAccessFile randomFile = new

RandomAccessFile("/sdcard/acc.txt", "rw");

// The length of the file (the number of bytes)

long fileLength = randomFile.length();

// Move the file pointer to the end of the file

randomFile.seek(fileLength);

randomFile.writeBytes(a);

randomFile.close();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

Layout files

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<CheckedTextView

android:id="@+id/AT"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="@string/AT"

android:textSize="20dp" />

<CheckedTextView

android:id="@+id/onAccuracyChanged"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="@string/onAccuracyChanged"

android:textSize="18dp" />

<LinearLayout

android:layout_width="fill_parent"

android:layout_height="wrap_content" >

<Button

android:id="@+id/Button_Write"

android:layout_width="90dp"

android:layout_height="wrap_content"

android:text="@string/Button_Write"

android:textSize="20dp"/>

<Button

android:id="@+id/Button_Stop"

android:layout_width="90dp"

android:layout_height="wrap_content"

android:text="@string/Button_Stop" android:textSize="20dp"/>

</LinearLayout>

</LinearLayout>

String

<?xml version="1.0" encoding="utf-8"?>

<resources>

<string name="hello">Hello World, PracticeActivity!</string>

<string name="app_name">Practice</string>

<string name="onAccuracyChanged">onAccuracyChanged doesn’t

detonate</string>

<string name="AT">0</string>

<string name="Button_Write">Write</string>

<string name="Button_Stop">Stop</string>

</resources>

(2) Step counting method

There are many mobile step‐counting methods but the best method is not

found now. A typical acceleration scalar graph is showed below.

Self‐designed methods are encouraged in this step and the display of the results

on the screen in real time is required.

Hint

We can use the threshold filtering method. When the acceleration is higher or

lower than the threshold, we can treat it as a step’s beginning or ending. We also

need to consider the waveform burr and the acceleration of walking is not a simple

single‐peak waveform.

3. Questions

(1) Why we need low pass filtering when we measure the acceleration ?

What are the differences made by the filtering? Make a contrast.

(2) Can we estimate the stride length using the acceleration oscillogram?

(3) What’s the meaning of using super.onPause ?

4. Extended problems

(1) Suppose a driver uses an Android mobile.Use the GPS data and acceleration data

to judge the switch of the moving and rest states and upload the status

information to the server.

(2) Suppose there are a great number of drivers using the app mentioned in the 1st

problem.How could we judge the traffic light’s color using these

information? Design and build a system to realize this function

Hint

You can refer the literature

Yiran Zhao, Yang Zhang, Tuo Yu, Tianyuan Liu, Xinbing Wang, Xiaohua Tian, Xue

Liu, “CityDrive: A map-generating and speed-optimizing driving system,” in

proceedings of IEEE International Conference on Computer Communications, pp.

1986-1994, 2014.