How to pass variables from one Activity to another in Android

How to pass variables from one Activity to another in Android

Think of a screnario where you are required to pass variables from one Activity to another.For example ,variables entered in a simple login activity are passed to another activity that uses the variables to connect to a database.
I will illustrate using code how you can pass variables from one activity to another.

How to pass variables between two activities.

Let have a MainActivity class that has three textfields.These fields,name,email and message texts while be entered.

Below is the MainActivity Code.

 package net.techoverload.myfirstapp;  
 import android.content.Intent;  
 import android.support.v7.app.AppCompatActivity;  
 import android.os.Bundle;  
 import android.view.View;  
 import android.widget.EditText;  
 public class MainActivity extends AppCompatActivity {  
   public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";  
   public final static String EXTRA_NAME="com.example.myfirstapp.NAME";  
   public final static String EXTRA_EMAIL="com.example.myfirstapp.EMAIl";  
   @Override  
   protected void onCreate(Bundle savedInstanceState) {  
     super.onCreate(savedInstanceState);  
     setContentView(R.layout.activity_main);  
   }  
   //This method will be called once the user clicks send message button  
   public void sendText(View view) {  
     Intent intent = new Intent(this, DisplayActivity.class); //Start the intent  
     EditText editTextMessage = (EditText) findViewById(R.id.edit_message); //get variables from textviews  
     EditText editTextName = (EditText) findViewById(R.id.enter_name);  
     EditText editTextEmail = (EditText) findViewById(R.id.enter_email);  
     String message = editTextMessage.getText().toString(); //convert to string variables  
     String name = editTextName.getText().toString();//convert to string variables  
     String email = editTextEmail.getText().toString();//convert to string variables  
     intent.putExtra(EXTRA_MESSAGE,message); //put variables in an intent  
     intent.putExtra(EXTRA_NAME,name);  
     intent.putExtra(EXTRA_EMAIL,email);  
     startActivity(intent);  
   }  
 }  

Explanation:

In the above code,I have created Intent object and named it intent.Using intent.putExtra() method i added all the three string values name,email and message to my intent.

Its time now to create next activity and get our variables that we passed.

 package net.techoverload.myfirstapp;  
 import android.content.Intent;  
 import android.support.v7.app.AppCompatActivity;  
 import android.os.Bundle;  
 import android.view.ViewGroup;  
 import android.widget.TextView;  
 import org.w3c.dom.Text;  
 public class DisplayActivity extends AppCompatActivity {  
   @Override  
   protected void onCreate(Bundle savedInstanceState) {  
     super.onCreate(savedInstanceState);  
     setContentView(R.layout.activity_display);  
     Intent intent=getIntent();  
     String name=intent.getStringExtra(MainActivity.EXTRA_NAME);  
     String email=intent.getStringExtra(MainActivity.EXTRA_EMAIL);  
     String message=intent.getStringExtra(MainActivity.EXTRA_MESSAGE);  
     TextView nameView=new TextView(this);  
     nameView.setTextSize(20);  
     nameView.setText(name);  
     TextView emailView=new TextView(this);  
     emailView.setTextSize(20);  
     emailView.setText(email);  
     TextView messageView=new TextView(this);  
     messageView.setTextSize(20);  
     messageView.setText(message);  
     ViewGroup layout=(ViewGroup)findViewById(R.id.activity_display);  
     layout.addView(nameView);  
     layout.addView(emailView);  
     layout.addView(messageView);  
   }  
 }