Mithat Konar (the wiki)

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====== Chapter 3 notes ======

===== Keyboard shortcuts for emulators =====
There's no obvious way to do things like push power and volume buttons on an AVD. You can use keyboard shortcuts to do these kinds of things. The [[http://developer.android.com/tools/help/emulator.html#KeyMapping|official Android documentation]] misses some of the available shortcuts; the list at [[http://www.shortcutworld.com/en/win/Android-Emulator.html|shortcutworld.com]] is more complete.

Genymotion shortcuts are listed in the [[https://www.genymotion.com/#!/developers/user-guide|user guide]] under "Keyboard Shortcuts". I wasn't able to find documentation for Visual Studio Emulator for Android's keyboard shortcuts.
===== p. 75: Project properties =====
  * App Name: ''Messenger''((As though there weren't enough apps named "Messenger" already. :-/))
  * Company Domain: ''hfad.com''
  * Activity Name: ''CreateMessageActivity''
  * Layout Name: ''activity_create_message''

===== p. 76: Code block =====
<code XML>
<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="16dp"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:paddingTop="16dp"
tools:context=".CreateMessageActivity" >
<Button
    android:id="@+id/send"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:layout_marginLeft="36dp"
    android:layout_marginTop="21dp"
    android:onClick="onSendMessage"
    android:text="@string/send" />
<EditText
    android:id="@+id/message"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/send"
    android:layout_below="@+id/send"
    android:layout_marginTop="18dp"
    android:ems="10" />
</RelativeLayout>
</code>

===== p. 77: Code block =====
<code java>
package com.hfad.messenger;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;

public class CreateMessageActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_create_message);
    }

    //Call onSendMessage() when the button is clicked
    public void onSendMessage(View view) {
    }
}
</code>

===== A note about these code blocks!! =====
<WRAP center round important 60%>
Heads up!!!
</WRAP>

You may have noticed that our apps up to now don't show an app name at the top of the screen. This is due to (once again) the way newer Android Studio generates files compared to the version used in //HFAD//.

If we stick to the files generated by Android Studio and //modify// them rather than replacing them outright, we'll have better results. Here's the default ''contact_create_message.xml'' file as generated by Android Studio 1.5.1 and after I removed the TextView and added the Button and TextEdit from the code in //HFAD//:

<file xml contact_create_message.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"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:showIn="@layout/activity_create_message"
    tools:context="com.hfad.messenger2.CreateMessageActivity">

    <Button
        android:id="@+id/send"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="36dp"
        android:layout_marginTop="21dp"
        android:onClick="onSendMessage"
        android:text="@string/send" />
    <EditText
        android:id="@+id/message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/send"
        android:layout_below="@+id/send"
        android:layout_marginTop="18dp"
        android:ems="10" />
</RelativeLayout>
</file>

It's almost identical to the version in //HFAD//, but the small differences in the first 14 or so lines the top are important.

Differences with ''CreateMessageActivity.java'' are more substantial. Here is the ''CreateMessageActivity.java'' file as created by Android Studio 1.5.1 but with the addition of a stub for the ''onSendMessage'' handler.

<file java CreateMessageActivity.java>
package com.hfad.messenger;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;

public class CreateMessageActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_create_message);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

       FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_create_message, 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();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
    
    // Call onSendMessage when the button is clicked.
    public void onSendMessage(View view) {
    }
}
</file>

If you look over this version of ''CreateMessageActivity.java'', you can probably figure out which lines of code are introducing the interface features. I will continue to use this version of the file throughout this chapter and approach future projects in a similar way.

===== p. 78: Create a second activity =====
The create activity screen should look like this:\\
{{:android_learning:headfirst_android_development_notes:ch3-create-second-activity.png?direct&640|}}

When you click "Finish" Android Studio will create //two// new layout files:
  * ''activity_receive_message.xml''
  * ''content_receive_message.xml''

As we have seen before, ''activity_receive_message.xml'' is the wrapper and ''content_receive_message.xml'' has the content that we're actually interested in. 

<WRAP center round tip 90%>
Remember: edit ''content_{whatever}.xml'' files. Leave ''activity_{whatever}.xml'' files alone.
</WRAP>

===== pp. 85-87 Codecheck 1 =====
The app through p. 87.
{{youtube>QFJ7TkLZ1C4?600x360&rel=0}}
\\

===== p. 89 =====

The Pool Puzzle is challenging, but try to do it without looking at the solution on p. 90. Start by thinking about the logic that needs to happen, then write the code. 

===== p. 91 =====

The code on p. 91 refers to a constant ''ReceiveMessageActivity.EXTRA_MESSAGE''. When you add this to the editor, Android Studio will get angry and tell you it doesn't exist. You will create the constant later when you edit ''ReceiveMessageActivity.java''.

===== p. 92 =====
Do //**not**// replace the contents of ''ReceiveMessageActivity.java'' with the code from the book. Instead, figure out where in the code generated by Android Studio to place the following code snippets:
<code java>
public static final String EXTRA_MESSAGE = "message";
</code>

<code java>
Intent intent = getIntent();
String messageText = intent.getStringExtra(EXTRA_MESSAGE);
TextView messageView = (TextView)findViewById(R.id.message);
messageView.setText(messageText);
</code>

Make sure to add the needed ''import'' statements as well.

===== p. 94: Codecheck 2 =====
The app through p. 94.
{{youtube>EuVQxeIiMJw?600x360&rel=0}}
\\

===== p. 97 =====
You can find a list of common intents (what the book calls standard actions) in the official [[http://developer.android.com/guide/components/intents-common.html
|Developer documentumentation]]. The documentation also shows you what ''Intent.EXTRA_{whatever}''s you can set for each common intent using the ''putExtra'' method.

===== p. 98: Codecheck 3 =====
The app through p. 98.
{{youtube>rml-Ptbn2J8?600x360&rel=0}}
\\

===== p. 105 =====

Windows users, before you try to run your app on a real device, make sure you have the [[|necessary driver]] installed. If you are using a Nexus device, you should be able to use the Google USB Driver available in //Tools > Android > SDK Manager// on the //SDK Tools// tab.\\
{{:android_learning:headfirst_android_development_notes:google-usb-driver.png?direct&640|}}

Mac and Linux users won't need additional drivers.

===== p. 111: Finished =====
{{youtube>W-v1ZbDfPJc?600x360&rel=0}}
\\

===== p. 114 =====

Add this to the bullet points:
  * An Android app is a collection of **Activities**.
  * You move from Activity to Activity, whether within your app or in another app, via **Intent**s.
  * Intents can be //explicit// or //implicit//.
  * Actions are used to specify standard operations with implicit Intents.