Intents in Android

Introduction

 

Intents are requests from an activity to another activity. In Android, activity means a single page for implementing elements on it. An Intent is an asynchronous message that sends values from one component to another component of 2 different activities. It is mainly used for starting an activity from another activity.

 

 

Declaration

android.content.Intent intent =new intent(parameters);

This defines the source to the destination.

 

startActivity(intent);

This starts the activity to transfer the values and the request to another activity.

 

Types Of Intents

 

Android supports implicit and explicit Intent.

 

Implicit Intent: Specify an action from the current activity to another. It uses built-in applications to perform the task.

Intent i = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.google.com"));
startActivity(i);

According to this example when we use this intent then the web browser automatically opens and searches Google. In other words, the current activity transfers the link on the web browser for the search.

 

ACTION_VIEW show action.

 

The following are all the Basic Actions:

ACTION_MAIN
ACTION_VIEW
ACTION_ATTACH_DATA
ACTION_EDIT
ACTION_PICK
ACTION_CHOOSER
ACTION_GET_CONTENT
ACTION_DIAL
ACTION_CALL
ACTION_SEND
ACTION_SENDTO
ACTION_ANSWER
ACTION_INSERT
ACTION_DELETE
ACTION_RUN
ACTION_SYNC
ACTION_PICK_ACTIVITY
ACTION_SEARCH
ACTION_WEB_SEARCH
ACTION_FACTORY_TEST

Ther action will be used depending on their format like:

ACTION_VIEW -> Uri.parse(http://www.google.com);
ACTION_DIAL ->Uri.parse(“tel:[phone]”);

123456789 is contact Number.

 

Explicit Intent

Intent i1 =new Intent(FirstMainActivity.this,SecondMainActivity.class);
String username="Neeraj";
String password="Neeraj";
i1.putExtra("Username", username);
i1.putExtra("Password", password);
startActivity(i1);

This example shows two activities, one is “FirstMainActivity” and the other is “SecondMainActivity”.

 

“FirstMainActivity,this” means the current activity that sends values.

 

The “SecondmainActivity.class” means another activity that gets values.

 

So the preceding example shows the transfer of values from the current activity to another activity.

 

How to get Values in another Activity from an Intent?

 

When we use an Intent to send a value from one activity to another then we use a “Bundle”. A Bundle receives a component from previous activity.

Demo Example of Login

 

FirstMainActivity.java file code,

package com.example.logindemo;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class FirstMainActivity extends Activity {
    Button b;
    EditText user;
    EditText pass;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_first_main);

        b = (Button) findViewById(R.id.b1);
        user = (EditText) findViewById(R.id.t1);
        pass = (EditText) findViewById(R.id.t2);

        b.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                if (user.getText().toString().equals("Neeraj")
                        && pass.getText().toString().equals("Neeraj")) {
                    Toast.makeText(FirstMainActivity.this,
                            "Successfully Login", Toast.LENGTH_SHORT).show();

                    Intent i = new Intent(FirstMainActivity.this,
                            SecondMainActivity.class);
                    i.putExtra("User", user.getText().toString());
                    i.putExtra("Pass", pass.getText().toString());
                    user.setText("");
                    pass.setText("");
                    startActivity(i);
                } else {
                    Toast.makeText(FirstMainActivity.this, "Invalid",
                            Toast.LENGTH_SHORT).show();
                    user.setText("");
                    pass.setText("");
                }
            }
        });
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.first_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();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

SecondMainActivity.java file Code,

package com.example.logindemo;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.TextView;
public class SecondMainActivity extends Activity {
    TextView tv1, tv2;
    Button b;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second_main);
        Bundle bundle = getIntent().getExtras();
        b = (Button) findViewById(R.id.fill);
        String user = bundle.getString("User");
        String pass = bundle.getString("Pass");
        tv1 = (TextView) findViewById(R.id.v1);
        tv2 = (TextView) findViewById(R.id.v2);
        tv1.setText(user);
        tv2.setText(pass);
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.second_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();
        if (id == R.id.action_settings)
        {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}