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 Intents.

Implicit Intent: Specify an action from the current activity to another. It uses builtin 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 automatic 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:

1. ACTION_MAIN
2. ACTION_VIEW
3. ACTION_ATTACH_DATA
4. ACTION_EDIT
5. ACTION_PICK
6. ACTION_CHOOSER
7. ACTION_GET_CONTENT
8. ACTION_DIAL
9. ACTION_CALL
10. ACTION_SEND
11. ACTION_SENDTO
12. ACTION_ANSWER
13. ACTION_INSERT
14. ACTION_DELETE
15. ACTION_RUN
16. ACTION_SYNC
17. ACTION_PICK_ACTIVITY
18. ACTION_SEARCH
19. ACTION_WEB_SEARCH
20. 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 a previous activity.

Bundle bundle1 = getIntent().getExtras();
String username = bundle1.getString("Username");
String password = bundle1.getString("Password");

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);
    }
}