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--- android_learning:headfirst_android_development_notes:chapter_5 [2016/01/24 00:34] – mithat
+++ android_learning:headfirst_android_development_notes:chapter_5 [2016/01/24 04:45] (current) – [Additional notes] mithat
@@ Line 1: / Line 1: @@
-<WRAP center round info 60%>
-Under development.
-</WRAP>
 ====== Chapter 5 notes ======
@@ Line 33: / Line 29: @@
 ===== pp. 174 =====
-Create a new project called "Linear Layout Demo" to experiment with the changes described in this section. Call the main activity, "Send Message". After creating the default project, you will need to convert the main RelativeLayout to a LinearLayout. One way to do this is:
+Create a new project called "Linear Layout Demo" to experiment with the changes described in this section. Call the main activity, "SendMessageActivity". After creating the default project, you will need to convert the main RelativeLayout to a LinearLayout. One way to do this is:
   - Open ''content_send_message.xml'' in Text mode.
@@ Line 48: / Line 44: @@
 <WRAP center round tip 90%>
-**So, what's the difference between ''android:gravity'' and ''android:layout_gravity''?**
+**What's the difference between\\ ''android:gravity'' and ''android:layout_gravity''?**
   * ''android:gravity'' specifies where the //View's contents// should be placed within the View.
-  * ''android:layout_gravity'' specifies where the //View itself// should be placed inside its parent.
+  * ''android:layout_gravity'' specifies where the //View itself// should be placed within its parent.
 A Subtle, but important, distinction.
 </WRAP>
+But now we have a new problem: the email icon, which is actually part of a FloatingActionBar that Android Studio adds to all default projects, is covering the Send button. [[http://code2care.org/2015/how-to-remove-floating-action-button-android-studio-blank-activity-template/|This page]] at Code2care.org shows you how to get rid of the FloatingActionBar altogether by following the procedure. I'm duplicating that content here in case the original goes away:
-===== Additional notes =====
+  - In the ''{Whatever}Activity.java'' file, remove the code that creates the FloatingActionBar inside the ''onCreate'' method:<code java>
-After all this, you might be wondering why you don't just use the drag-and-drop UI builder on the "Design" tab for everything rather than code by hand. The answer is twofold:
+FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
-  - Crawl before you walk. To use the UI builder effectively, you need to know what it is doing.
+fab.setOnClickListener(new View.OnClickListener() {
-  - The UI builder only gets you so far. Typically you need to change the code that the UI builder generated for you. So you need to know what the code does.
+	@Override
+	public void onClick(View view) {
+		Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
+				.setAction("Action", null).show();
+	}
+});</code>
+  - In the ''activity_{whatever}.xml'' layout file, remove the ''android.support.design.widget.FloatingActionButton'' item:<code xml>
+<android.support.design.widget.FloatingActionButton
+	android:id="@+id/fab"
+	android:layout_width="wrap_content"
+	android:layout_height="wrap_content"
+	android:layout_gravity="bottom|end"
+	android:layout_margin="@dimen/fab_margin"
+	android:src="@android:drawable/ic_dialog_email" /></code>
+===== p. 191 =====
+Create a new project to work with the GridLayout example. The process of converting the default RelativeLayout to a GridLayout is similar to changing it to a LinearLayout. Be sure to add an ''android:columnCount'' attribute.
+===== p. 193 =====
+When you create the EditText for the GridLayout example, add and remove the ''android:layout_gravity'' attribute to gain an understanding of what it does.
+===== p. 205 =====
+Create a throwaway project for this final section of the chapter and experiment with as many of the Views covered as possible.
+===== p. 215 =====
+A good source of images that you can use without worrying about licensing is [[https://openclipart.org/|openclipart.org]]. Don't expect production-quality images though.
+Another good resource is, [[https://www.iconfinder.com/|iconfinder.com]], but you have to take care to meet the licensing requirements of each image.
+<WRAP center round tip 90%>
+**Be careful about file names.**\\ Image file names can only have lowercase letters, numbers, and the underscore in them.
+</WRAP>
+===== p. 219 =====
+Your text suggest a ScrollView can be used as a root ViewGroup:
+<file xml content_main.xml>
+<?xml version="1.0" encoding="utf-8"?>
+<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    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.hfad.scrollviewdemo.MainActivity"
+    tools:showIn="@layout/activity_main">
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical">
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="Top!" />
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="Hello World!" />
+        ...
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="Bottom!" />
+    </LinearLayout>
+</ScrollView>
+</file>
+However, in my experience this leads to unpredictable results (top of the ScrollView being obscured, etc.). A more reliable strategy seems to be nesting a ScrollView inside a root ViewGroups:
+<file xml content_main.xml>
+<?xml version="1.0" encoding="utf-8"?>
+<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    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"
+    app:layout_behavior="@string/appbar_scrolling_view_behavior"
+    tools:context="com.hfad.scrollviewdemo.MainActivity"
+    tools:showIn="@layout/activity_main">
+    <TextView
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="Outside ScrollView"
+        android:id="@+id/textView" />
+    <ScrollView
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:id="@+id/scrollView"
+        android:layout_below="@+id/textView">
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="vertical">
+            <TextView
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:text="Top" />
+            <TextView
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:text="Hello World!" />
+            ...
+            <TextView
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:text="Bottom" />
+        </LinearLayout>
+    </ScrollView>
+</RelativeLayout>
+</file>
+Android Studio produces a warning stating that the ''android:layout_height'' attribute of the LinearLayout inside the ScrollView should be set to ''wrap_content'' rather than ''match_parent''.
+<WRAP center round info 90%>
+In the examples above, I am using string literals for the text attributes---only because this is throwaway, quick-n-dirty, prove-a-concept code.
+</WRAP>
+===== Additional notes on the UI builder =====
+If you examine the UI builder on a layout's "Design" tab, you will see that in addition to using it to add Views to your layout, you can also edit your Views' attributes.
+Given that for a lot of people pointing, clicking, dragging, and dropping is more fun than writing code, you might be wondering why we didn't just use the drag-and-drop UI builder on the "Design" tab for everything rather than coding by hand. The answer is twofold:
+  - Crawl before you walk. To use the UI builder effectively, you need to know what it is doing.
+  - The UI builder only gets you so far. Typically you need to change the code that the UI builder generates for you. So you need to know what the code does.