Android - Wi-Fi Tutorial

2021-12-07 13:59 Android开发

Android allows applications to access to view the access the state of the wireless connections at very low level. Application can access almost all the information of a wifi connection. The information that an application can access includes connected network's link speed,IP address, negotiation state, other networks information. Applications can also scan, add, save, terminate and initiate Wi-Fi connections. Android providesWifiManagerAPI to manage all aspects of WIFI connectivity. We can instantiate this class by callinggetSystemServicemethod. Its syntax is given below − <pre class="prettyprint notranslate prettyprinted" > WifiManager mainWifiObj; mainWifiObj = (WifiManager) getSystemService(Context.WIFI_SERVICE); </pre> In order to scan a list of wireless networks, you also need to register your BroadcastReceiver. It can be registered usingregisterReceivermethod with argument of your receiver class object. Its syntax is given below − <pre class="prettyprint notranslate prettyprinted" > class WifiScanReceiver extends BroadcastReceiver { public void onReceive(Context c, Intent intent) { } } WifiScanReceiver wifiReciever = new WifiScanReceiver(); registerReceiver(wifiReciever, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION)); </pre> The wifi scan can be start by calling thestartScanmethod of the WifiManager class. This method returns a list of ScanResult objects. You can access any object by calling thegetmethod of list. Its syntax is given below − <pre class="prettyprint notranslate prettyprinted" > List<ScanResult> wifiScanList = mainWifiObj.getScanResults(); String data = wifiScanList.get(0).toString();</pre> Apart from just Scanning, you can have more control over your WIFI by using the methods defined in WifiManager class. They are listed as follows − <table class="table table-bordered" > <tbody > <tr > <th >Sr.No</th> <th >Method & Description</th> </tr> <tr > <td >1</td> <td >addNetwork(WifiConfiguration config) This method add a new network description to the set of configured networks. </td> </tr> <tr > <td >2</td> <td >createWifiLock(String tag) This method creates a new WifiLock. </td> </tr> <tr > <td >3</td> <td >disconnect() This method disassociate from the currently active access point. </td> </tr> <tr > <td >4</td> <td >enableNetwork(int netId, boolean disableOthers) This method allow a previously configured network to be associated with. </td> </tr> <tr > <td >5</td> <td >getWifiState() This method gets the Wi-Fi enabled state </td> </tr> <tr > <td >6</td> <td >isWifiEnabled() This method return whether Wi-Fi is enabled or disabled. </td> </tr> <tr > <td >7</td> <td >setWifiEnabled(boolean enabled) This method enable or disable Wi-Fi. </td> </tr> <tr > <td >8</td> <td >updateNetwork(WifiConfiguration config) This method update the network description of an existing configured network. </td> </tr> </tbody> </table> <h2 >Example</h2> Here is an example demonstrating the use of WIFI. It creates a basic application that scans a list of wireless networks and populate them in a list view. To experiment with this example, you need to run this on an actual device on which wifi is turned on. <table class="table table-bordered" > <tbody > <tr > <th >Steps</th> <th >Description</th> </tr> <tr > <td >1</td> <td >You will use Android studio to create an Android application under a package com.example.sairamkrishna.myapplication. While creating this project, make sure you Target SDK and Compile With at the latest version of Android SDK to use higher levels of APIs.</td> </tr> <tr > <td >2</td> <td >Modify src/MainActivity.java file to add WebView code.</td> </tr> <tr > <td >3</td> <td >Modify the res/layout/activity_main to add respective XML components</td> </tr> <tr > <td >4</td> <td >Modify the AndroidManifest.xml to add the necessary permissions</td> </tr> <tr > <td >5</td> <td >Run the application and choose a running android device and install the application on it and verify the results.</td> </tr> </tbody> </table> Following is the content of the modified main activity filesrc/MainActivity.java. <pre class="prettyprint notranslate prettyprinted" > package com.example.sairamkrishna.myapplication; import android.app.Activity; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.graphics.Color; import android.net.wifi.ScanResult; import android.net.wifi.WifiManager; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.EditText; import android.widget.ListView; import android.widget.TextView; import android.widget.Toast; import java.util.List; public class MainActivity extends Activity { ListView lv; WifiManager wifi; String wifis[]; WifiScanReceiver wifiReciever; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); lv=(ListView)findViewById(R.id.listView); wifi=(WifiManager)getSystemService(Context.WIFI_SERVICE); wifiReciever = new WifiScanReceiver(); wifi.startScan(); } protected void onPause() { unregisterReceiver(wifiReciever); super.onPause(); } protected void onResume() { registerReceiver(wifiReciever, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION)); super.onResume(); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.menu_main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); //noinspection SimplifiableIfStatement if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } private class WifiScanReceiver extends BroadcastReceiver{ public void onReceive(Context c, Intent intent) { List<ScanResult> wifiScanList = wifi.getScanResults(); wifis = new String[wifiScanList.size()]; for(int i = 0; i < wifiScanList.size(); i++){ wifis[i] = ((wifiScanList.get(i)).toString()); } lv.setAdapter(new ArrayAdapter<String>(getApplicationContext(),android.R.layout.simple_list_item_1,wifis)); } } }</pre> Following is the modified content of the xmlres/layout/activity_main.xml. <pre class="prettyprint notranslate prettyprinted" > <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"> <TextView android:text="Wifi" android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/textview" android:textSize="35dp" android:layout_alignParentTop="true" android:layout_centerHorizontal="true" /> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Tutorials point" android:id="@+id/textView" android:layout_below="@+id/textview" android:layout_centerHorizontal="true" android:textColor="#ff7aff24" android:textSize="35dp" /> <mageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/imageView" android:src="@drawable/abc" android:layout_below="@+id/textView" android:layout_centerHorizontal="true" /> <ListView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/listView" android:layout_below="@+id/imageView" android:layout_alignParentLeft="true" android:layout_alignParentStart="true" android:background="#fff5d376" /> </RelativeLayout></pre> Following is the content ofAndroidManifest.xmlfile. <pre class="prettyprint notranslate prettyprinted" > <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.sairamkrishna.myapplication" > <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" /> <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" /> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name=".MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest></pre> Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from Android studio, open one of your project's activity files and click Run<img alt="Eclipse Run Icon" class="inline" src="http://www.tutorialspoint.com/android/images/eclipse_run.jpg" />icon from the toolbar. Before starting your application, Android studio will display following window to select an option where you want to run your Android application. <img alt="Anroid Wi-Fi Tutorial" src="http://www.tutorialspoint.com/android/images/choose_device.jpg" /> Select your mobile device as an option and then check your mobile device which will display your mobile screen filled with wireless networks around you. It is shown below − <img alt="Anroid Wi-Fi Tutorial" src="http://www.tutorialspoint.com/android/images/wifi.jpg" /> Note the information that has been returned to you. It contains much information about each of the wireless network detected. <img alt="android_wifi_tutorials" src="http://www.tutorialspoint.com/android/images/wifi1.jpg" /> Above image shows different wifi connections which are connected with your devices