Widget attributes
Let’s go over some of the attributes that you have used to configure your widgets.
android:layout_width and android:layout_height
The android:layout_width and android:layout_height attributes are required for almost every type of widget. They are typically set to either match_parent or wrap_content:
match_parent view will be as big as its parent
wrap_content view will be as big as its contents require
(You may see fill_parent in some places. This deprecated value is equivalent to match_parent.)
For the root LinearLayout, the value of both the height and width attributes is match_parent. The
LinearLayout is the root element, but it still has a parent – the view that Android provides for your app’s view hierarchy to live in.
The other widgets in your layout have their widths and heights set to wrap_content. You can see in Figure 1.10 how this determines their sizes.
The TextView is slightly larger than the text it contains due to its android:padding="24dp" attribute.
This attribute tells the widget to add the specified amount of space to its contents when determining its size. You are using it to get a little breathing room between the question and the buttons. (Wondering about the dp units? These are density-independent pixels that you will learn about in Chapter 8.)
android:orientation
The android:orientation attribute on the two LinearLayout widgets determines whether their children will appear vertically or horizontally. The root LinearLayout is vertical; its child LinearLayout is horizontal.
The order in which children are defined determines the order in which they appear on screen. In a vertical
LinearLayout, the first child defined will appear topmost. In a horizontal LinearLayout, the first child
defined will be leftmost. (Unless the language of the device is a language that runs right-to-left, such as Arabic or Hebrew. In that case, the first child will be rightmost.)
android:text
The TextView and Button widgets have android:text attributes. This attribute tells the widget what text to display.
Notice that the values of these attributes are not literal strings. They are references to string resources.
Astring resource is a string that lives in a separate XMLfile called a strings file. You can give a widget a hard-coded string, like android:text="True", but it is usually not a good idea. Placing strings into a separate file and then referencing them is better because it makes localization easy.
The string resources you are referencing in activity_quiz.xml do not exist yet. Let’s fix that.
Let’s go over some of the attributes that you have used to configure your widgets.
android:layout_width and android:layout_height
The android:layout_width and android:layout_height attributes are required for almost every type of widget. They are typically set to either match_parent or wrap_content:
match_parent view will be as big as its parent
wrap_content view will be as big as its contents require
(You may see fill_parent in some places. This deprecated value is equivalent to match_parent.)
For the root LinearLayout, the value of both the height and width attributes is match_parent. The
LinearLayout is the root element, but it still has a parent – the view that Android provides for your app’s view hierarchy to live in.
The other widgets in your layout have their widths and heights set to wrap_content. You can see in Figure 1.10 how this determines their sizes.
The TextView is slightly larger than the text it contains due to its android:padding="24dp" attribute.
This attribute tells the widget to add the specified amount of space to its contents when determining its size. You are using it to get a little breathing room between the question and the buttons. (Wondering about the dp units? These are density-independent pixels that you will learn about in Chapter 8.)
android:orientation
The android:orientation attribute on the two LinearLayout widgets determines whether their children will appear vertically or horizontally. The root LinearLayout is vertical; its child LinearLayout is horizontal.
The order in which children are defined determines the order in which they appear on screen. In a vertical
LinearLayout, the first child defined will appear topmost. In a horizontal LinearLayout, the first child
defined will be leftmost. (Unless the language of the device is a language that runs right-to-left, such as Arabic or Hebrew. In that case, the first child will be rightmost.)
android:text
The TextView and Button widgets have android:text attributes. This attribute tells the widget what text to display.
Notice that the values of these attributes are not literal strings. They are references to string resources.
Astring resource is a string that lives in a separate XMLfile called a strings file. You can give a widget a hard-coded string, like android:text="True", but it is usually not a good idea. Placing strings into a separate file and then referencing them is better because it makes localization easy.
The string resources you are referencing in activity_quiz.xml do not exist yet. Let’s fix that.
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