In this lesson we will:

 - pass data using Intent

Translated by Taras Leskiv (http://android-by-example.blogspot.com/)

In the previous lessons we found out what an Intent is and how to use it. We have invoked one Activity from another passing an action. Now we will learn how to transfer data. We will make the simplest application. On the first screen we will enter our name and surname and the second screen will display this data. We will transfer data inside Intent.

Let’s create a project:

Project name: P0281_IntentExtras
Build Target: Android 2.3.3
Application name: IntentExtras
Package name: ru.startandroid.develop.p0281intentextras
Create Activity: MainActivity

Open main.xml and draw a screen with fields and send button:

<?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">
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:gravity="center_horizontal"
        android:text="Input your Name">
    </TextView>
    <TableLayout
        android:id="@+id/tableLayout1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:stretchColumns="1">
        <TableRow
            android:id="@+id/tableRow1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <TextView
                android:id="@+id/textView1"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="First Name">
            </TextView>
            <EditText
                android:id="@+id/etFName"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="5dp">
                <requestFocus>
                </requestFocus>
            </EditText>
        </TableRow>
        <TableRow
            android:id="@+id/tableRow2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <TextView
                android:id="@+id/textView2"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Last Name">
            </TextView>
            <EditText
                android:id="@+id/etLName"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="5dp">
            </EditText>
        </TableRow>
    </TableLayout>
    <Button
        android:id="@+id/btnSubmit"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="Submit">
    </Button>
</LinearLayout>

We will enter name and surname into EditText and Submit button will invoke other screen and pass it this data.

Write code for MainAcitivty.java:

package ru.startandroid.develop.p0281intentextras;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity implements OnClickListener {
  
  EditText etFName;
  EditText etLName;
  
  Button btnSubmit;
  
  
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        etFName = (EditText) findViewById(R.id.etFName);
        etLName = (EditText) findViewById(R.id.etLName);
        
        btnSubmit = (Button) findViewById(R.id.btnSubmit);
        btnSubmit.setOnClickListener(this);
        
    }


  @Override
  public void onClick(View v) {
    Intent intent = new Intent(this, ViewActivity.class); 
    intent.putExtra("fname", etFName.getText().toString());
    intent.putExtra("lname", etLName.getText().toString());
    startActivity(intent);
  } 
}

Define input fields and a button. We assign button a listener - Activity (this). Let’s observe onClick method implementation. We create Intent using the class, not action. If you remember we started to get acquainted with Intent this way. I will remind - it means that the system will look through the manifest-file of our application and will display an Activity if it finds one with the same class. ViewActivity is not created yet, that’s why the code will be underlined in red. However, we can still save the file. We will create this Activity a little bit later and the error will disappear.

So the Intent has been created, let’s observe the code further. putExtra method is used. It has lots of varieties and is similar to put method for Map, that is, it adds a key-value pair to the object. First parameter is key(name), the second - value.

We’ve put two objects with names fname and lname into Intent. fname contains the value of etFName field, lname - value of the etLName field. The only thing left to do is to send the equipped Intent using startActivity method.

Let’s create the second Activity now. Let’s name it ViewActivity.

Create layout-file view.xml for it:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <TextView
        android:id="@+id/tvView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="20dp"
        android:text="TextView"
        android:textSize="20sp">
    </TextView>
</LinearLayout>

It is just a TextView here which will display the incoming data.

Create ViewActivity class. Write this code:

package ru.startandroid.develop.p0281intentextras;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;

public class ViewActivity extends Activity {
  
  TextView tvView;
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.view);
    
    tvView = (TextView) findViewById(R.id.tvView);
    
    Intent intent = getIntent();
    
    String fName = intent.getStringExtra("fname");
    String lName = intent.getStringExtra("lname");
    
    tvView.setText("Your name is: " + fName + " " + lName);
  }
}

Find TextView, then receive Intent and extract String objects with names fname and lname from it. These are the same objects, which we put inside in MainActivity.java. Form the output string into the TextView using the received data.

Don’t forget to register Activity inside manifest. This time we don’t need any intent filters as we know the name of Activity class and use the explicit invocation.

Save everything and run the application.

You will see the following screen:

Fill in the fields with whatever you wish. I will write John in the First Name field and Smith in the Last Name field. 

Press Submit:

ViewActivity is displayed, it read data from Intent and displayed it on the screen.

You can put not only String data inside Intent. In the list of Intent methods you can see all the types that putExtra method can receive as a parameter.

In the next lesson: 

- starting Activity and receiving a result