Java,Android,j2ee and jsp tutorials blog: android activity-JavaTyro

if you are developing an Android app you may already fetching information from internet. While doing so there is a chance that internet connection is not available on users handset. Hence its always a good idea to check the network state before performing any task that requires internet connection.
You might also want to check what kind of internet connection is available in handset. For example is wifi currently enabled? or is mobile data network is connected.

Check Internet Connection

Here is a simple code snippet that will help you identify what kind of internet connection a user has on her device.
First we need following permission in order to access network state. Add following permission to your AndroidManifest.xml file.
Permissions required to access network state:

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

Now check following utility class NetworkUtil. It has method getConnectivityStatus which returns an int constant depending on current network connection. If wifi is enabled, this method will return TYPE_WIFI. Similarly for mobile data network is returns TYPE_MOBILE. You got the idea!!
There is also method getConnectivityStatusString which returns current network state as a more readable string.
NetworkUtil.java

package net.viralpatel.network;

import android.content.Context;

import android.net.ConnectivityManager;

import android.net.NetworkInfo;

public class NetworkUtil {

    public static int TYPE_WIFI = 1;

    public static int TYPE_MOBILE = 2;

    public static int TYPE_NOT_CONNECTED = 0;

    public static int getConnectivityStatus(Context context) {

        ConnectivityManager cm = (ConnectivityManager) context

                .getSystemService(Context.CONNECTIVITY_SERVICE);

        NetworkInfo activeNetwork = cm.getActiveNetworkInfo();

        if (null != activeNetwork) {

            if(activeNetwork.getType() == ConnectivityManager.TYPE_WIFI)

                return TYPE_WIFI;

            if(activeNetwork.getType() == ConnectivityManager.TYPE_MOBILE)

                return TYPE_MOBILE;

        } 

        return TYPE_NOT_CONNECTED;

    }

    public static String getConnectivityStatusString(Context context) {

        int conn = NetworkUtil.getConnectivityStatus(context);

        String status = null;

        if (conn == NetworkUtil.TYPE_WIFI) {

            status = "Wifi enabled";

        } else if (conn == NetworkUtil.TYPE_MOBILE) {

            status = "Mobile data enabled";

        } else if (conn == NetworkUtil.TYPE_NOT_CONNECTED) {

            status = "Not connected to Internet";

        }

        return status;

    }

}

You can use this utility class in your android app to check the network state of the device at any moment.
Now this code will return you the current network state whenever the utility method is called. What if you want to do something in your android app when network state changes? Lets say when Wifi is disabled, you need to put your android app service to sleep so that it does not perform certain task. Now this is just one usecase. The idea is to create a hook which gets called whenever network state changes. And you can write your custom code in this hook to handle the change in network state.

Broadcast Receiver to handle changes in Network state

You can easily handle the changes in network state by creating your own Broadcast Receiver. Following is a broadcast receiver class where we handle the changes in network.
Check onReceive() method. This method will be called when state of network changes. Here we are just creating a Toast message and displaying current network state. You can write your custom code in here to handle changes in connection state.
NetworkChangeReceiver.java

package net.viralpatel.network;

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.widget.Toast;

public class NetworkChangeReceiver extends BroadcastReceiver {

    @Override

    public void onReceive(final Context context, final Intent intent) {

        String status = NetworkUtil.getConnectivityStatusString(context);

        Toast.makeText(context, status, Toast.LENGTH_LONG).show();

    }

}

Once we define our BroadcastReceiver, we need to define the same in AndroidMenifest.xml file. Add following to your menifest file.

<application  ...>

     ...

        <receiver

            android:name="net.viralpatel.network.NetworkChangeReceiver"

            android:label="NetworkChangeReceiver" >

            <intent-filter>

                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />

                <action android:name="android.net.wifi.WIFI_STATE_CHANGED" />

            </intent-filter>

        </receiver>

      ...

</application>

We defined our broadcast receiver class in menifest file. Also we defined two intent CONNECTIVITY_CHANGE and WIFI_STATE_CHANGED. Thus this will register our receiver for given intents. Whenever there is change in network state, android will fire these intents and our broadcast receiver will be called.
Below is complete AndroidMenifest.xml file.
AndroidMenifest.xml

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

    package="net.viralpatel.network"

    android:versionCode="1"

    android:versionName="1.0" >

    <uses-sdk

        android:minSdkVersion="8"

        android:targetSdkVersion="15" />

    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <application

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/AppTheme" >

        <receiver

            android:name="net.viralpatel.network.NetworkChangeReceiver"

            android:label="NetworkChangeReceiver" >

            <intent-filter>

                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />

                <action android:name="android.net.wifi.WIFI_STATE_CHANGED" />

            </intent-filter>

        </receiver>

    </application>

</manifest>

Run this demo in android emulator or actual device.
When Wifi is enabled, you’ll see a Toast message with message.
android-network-change-broadcast-wifi-enabled

android-network-change-broadcast-wifi-enabled

Now disable Wifi. The toast message will show you message that internet connection is not available.
android-network-change-broadcast-receiver-not-connected

android-network-change-broadcast-receiver-not-connected

Now enable mobile data network. The same will be show in toast message as soon as you enable mobile data connection.
android-data-connection-broadcast-receiver

android-data-connection-broadcast-receiver

Download Source Code

Browse through the source code in following Git repository:
GitHub: https://github.com/viralpatel/android-network-change-detect-example
Download complete source code:
Download: android-network-change-detect-example.zip (376 KB)

In Android, an activity is represent a single screen. Most applications have multiple activities to represent different screens, for example, one activity to display a list of the application settings, another activity to display the application status.

Note
Refer to this official Android activity article to understand more about Android activity.

In this tutorial, we show you how to interact with activity, when a button is clicked, navigate from current screen (current activity) to another screen (another activity).
P.S This project is developed in Eclipse 3.7, and tested with Android 2.3.3.

1. XML Layouts

Create following two XML layout files in “res/layout/” folder :

res/layout/main.xml – Represent screen 1
res/layout/main2.xml – Represent screen 2

File : res/layout/main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linearLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
 
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="I&apos;m screen 1 (main.xml)"
        android:textAppearance="?android:attr/textAppearanceLarge" />
 
    <Button
        android:id="@+id/button1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Click me to another screen" />
 
</LinearLayout>

File : res/layout/main2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linearLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >
 
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="I&apos;m screen 2 (main2.xml)"
        android:textAppearance="?android:attr/textAppearanceLarge" />
 
</LinearLayout>

2. Activities

Create two activity classes :

AppActivity.java –> main.xml
App2Activity.java –> main2.xml

To navigate from one screen to another screen, use following code :

    Intent intent = new Intent(context, anotherActivity.class);
    startActivity(intent);

File : AppActivity.java

package com.mkyong.android;
 
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Button;
import android.view.View;
import android.view.View.OnClickListener;
 
public class AppActivity extends Activity {
 
	Button button;
 
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		addListenerOnButton();
	}
 
	public void addListenerOnButton() {
 
		final Context context = this;
 
		button = (Button) findViewById(R.id.button1);
 
		button.setOnClickListener(new OnClickListener() {
 
			@Override
			public void onClick(View arg0) {
 
			    Intent intent = new Intent(context, App2Activity.class);
                            startActivity(intent);   
 
			}
 
		});
 
	}
 
}

File : App2Activity.java

package com.mkyong.android;
 
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
 
public class App2Activity extends Activity {
 
	Button button;
 
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main2);
	}
 
}

3. AndroidManifest.xml

Declares above two activity classes in AndroidManifest.xml.
File : AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.mkyong.android"
    android:versionCode="1"
    android:versionName="1.0" >
 
    <uses-sdk android:minSdkVersion="10" />
 
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:label="@string/app_name"
            android:name=".AppActivity" >
            <intent-filter >
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:label="@string/app_name"
            android:name=".App2Activity" >
        </activity>
    </application>
 
</manifest>

4. Demo

Run application.
AppActivity.java (main.xml) screen is display.

When above button is clicked, it will navigate to another screen App2Activity.java (main2.xml).

Add caption

Download Source Code

Download it – Android-From-Screen-To-Screen-Acticity-Example.zip (16 KB)

Tuesday 3 September 2013

Internet Connection Status & Network Change Receiver example in android

Check Internet Connection

Broadcast Receiver to handle changes in Network state

Download Source Code

Saturday 24 August 2013

Android Beginner: Android activity tutorial

1. XML Layouts

2. Activities

3. AndroidManifest.xml

4. Demo

Download Source Code

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