Intent In Android

Overview

We have seen in the previous articles about creating an environment for the development of Android Applications, and activity life cycles in Android Applications, etc. Kindly refer to the articles, given below:

1. Android Programming - Day One
2. Android Programming - Day Two 
3. How To Display A Dialog Window In Android
4. How To Display A Progress Dialog Window In Android  

Introduction

In this article, we will learn about Intent. An Android Application may have zero or more activities. When your application has more than one activity, you often need to navigate from the one activity to another activity. This is Intent, through which you navigate between the activities.

Coding

For this, create a new project IntentExampleApp. By default, MainActivity.java class is added in the project.

  

package com.example.administrator.intentexampleapp;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends ActionBarActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    @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);
    }
}

Add the second activity called MySecondActivity by right clicking on Java->New->Activity->Blank Activity.

  

 

 

As soon as a new activity is added in the project, the reference of the activity is also added in the AndroidManifest.xml file.

<?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.example.administrator.intentexampleapp" >

     <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>
         <activity
             android:name=".MySecondActivity"
             android:label="@string/title_activity_my_second" >
         </activity>
     </application>

 </manifest>

One more statement is added in this file.

<Intent-filter>
     <action android:name="android.intent.action.MySecondActivity" />
     <category android:name="android.intent.category.DEFAULT" />
 </Intent-filter>

This is used to invoke the second activity, using the name MySecondActivity. In the string.xml file under layout folder, add one string variable MySecond_Activity to be displayed as a text in the second activity.

<resources>
     <string name="app_name">IntentExampleApp</string>

     <string name="hello_world">Hello world!</string>
     <string name="Second_Activity">Click to show Second Activity</string>
     <string name="MySecond_Activity">This is my Second Activity</string>
     <string name="action_settings">Settings</string>
     <string name="title_activity_my_second">MySecondActivity</string>
 </resources>

In activity_main.xml file, add the method name showSecondActivity for onClick event and implement this method in MainActivity.java class file.

public void showSecondActivity(View v)
 {
      Intent intent= new Intent(this,MySecondActivity.class);
      startActivity(intent);
 }

Run the application by clicking Shift + F10.

 

When you click the button, the second activity opens.



Explanation

When the user clicks the button, the method showSecondActivity is called. In this method, an object of Intent is created and this is a type of an Explicit Intent. This Intent provides the external class to be invoked.The startActivity() method invokes another activity only. It does not return a result to the current activity.

Conclusion

In this article, we learned about Intent, which is of Explicit type. In the next article, I will explain about returning the results and passing the data from Intent object.