code_37-38_broadcasts.txt

Android Development Tutorial 37 and 38 - Broadcasting

***** Tutorial Notes
//Overview//
The goal here is to have one visible Activity send a broadcast Intent. Have a second invisible Activity receive the broadcast and post a Toast to acknowledge it consumed the intent. The UI is simply a Button that will use sendOutBroadcast() method, of the Activity class, to  send a broadcast intent. The mechanism that ties the sender and receiver together is the <intent-filter> <action> elements in the Manifest files.

NOTE: There are other broadcast methods like sendStickyBroadcast() or sendOrderedBroadcast(), that you can read about at http://developer.android.com/reference/android/content/Intent.html

//Tutorials//
** 37 - Sending Broadcast Intents
1. Start a new project named SendBroadcast
	a. Use the Empty Activity template
	b. Delete Hello World 
	c. Add Button, onClick = sendOutBroadcast
TIP! When setting properties in design view, click on the Properties toolbar and start typing, a hidden search box appears.
2. Main.java
	a. Import Intent and View
	b. Create sendOutBroadcast()
		i. Create implicit intent.

** 38 - Receiving Broadcast Intents
1. Start a new project, pick No Activity. NOTE: This generates the “NoFiles” gray screen.
2. Create a New>Other>Broadcast Receiver
	a. Name ReceiveBroadcast, with both Exported and Enabled options are selected.
NOTE: These settings allow the Android system to launch the receiver when needed and ensure that the class can receive messages sent by other applications on the device.
	b. Import Toast
	c. Make a Toast in the onReceive()
	3. Add an intent action filter, for the Receive activity, to the manifest.
4. First run the Receive activity but deselect launch default activity.

NOTE: I received the error "Could not identify launch activity: Default Activity not found". while Launching activity. Studio 2.0 did not popup the edit configurations when I clicked the Run icon. Instead I had to use the Run… on the Run Menu.

5. Now run the Send Broadcast Activity.
6. Test the applications.

///// Send Activity
***** manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.thenewboston.sendbroadcast">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

***** MainActivity.java
package com.thenewboston.sendbroadcast;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.content.Intent;
import android.view.View;

public class MainActivity extends AppCompatActivity {

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

    public void sendOutBroadcast(View view){
        Intent i = new Intent();// no explicit class like last tutorial
        i.setAction("com.thenewboston.sendbroadcast");// use package as a unique identifier.
        i.addFlags(Intent.FLAG_INCLUDE_STOPPED_PACKAGES); // for all versions of android
        sendBroadcast(i);
    }
}

***** activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.thenewboston.sendbroadcast.MainActivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="SEND BROADCAST"
        android:id="@+id/sendButton"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:onClick="sendOutBroadcast"
        android:nestedScrollingEnabled="false" />
</RelativeLayout>

///// ReceiveActivity
***** manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.thenewboston.receivebroadcast">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <receiver
            android:name=".ReceiveBroadcast"
            android:enabled="true"
            android:exported="true">

            <intent-filter>
                <action android:name="com.thenewboston.sendbroadcast">.</action>
            </intent-filter>
        </receiver>
    </application>
</manifest>

***** ReceiveBroadcast.java
package com.thenewboston.receivebroadcast;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class ReceiveBroadcast extends BroadcastReceiver {
    public ReceiveBroadcast() {
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"Broadcast has been received",Toast.LENGTH_LONG).show();
    }
}