LinearLayouts, TextViews and Drawables

I sent out a series of tweets today about LinearLayouts and unexpectedly, quite a few people like them. I decided to get off my lazy ass and actually write it down in a post for easy reference.

Let's start with the LinearLayout root view.  One of the most common things designers ask us to do is to put dividers in. Quick! Think! What should we do? Add a generic View for each divider? How about NO? Instead, we can delegate the task of displaying these dividers to the LinearLayout itself:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:orientation="vertical"
              android:layout_height="match_parent"
              android:divider="@drawable/divider_horizontal_dark"
              android:showDividers="middle">

Where divider_horizontal_dark can be anything you want to be the divider (I recommend using a shape):

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="rectangle" >
    <solid android:color="#24000000" />
    <size android:height="1dp" />
</shape>

Doing this prevents us from littering our view hierarchy with useless empty views. LinearLayout is actually extremely powerful, and a lot of the stuff most apps usually need is already built in. PS: For some reason I cannot find the showDividers attribute in the Android docs, but the available attributes are middle, beginning, end, none (or a combination of those). EDIT: +Nick Butcher showed us the light: docs here!

EDIT AGAIN: Nick has also lovingly pointed out that setShowDividers() was added in API 11. If by some cruel twist of fate you need to support anything below that, use LinearLayoutCompat. Also, you poor, poor thing.

Another common thing that we are asked to do is to have an image +  text displayed side by side. We use this quite a bit in the Domain app, most notably in the main navigation drawer:

Instead of having one huge RelativeLayout or (horror!) nested LinearLayouts, we can just have a bunch of TextViews in one LinearLayout.

You see, TextViews have this magical ability to add Drawables to themselves. You can position the Drawable anywhere you want, and even tint it from XML! :gasp:

Drawable placement can be in any of the cardinal directions (bottom, top, left, right) and the tint should be a defined colour in XML (not actually required, but encouraged. By me. I encourage it.). If the Drawable is too close to the text for your or your designer's taste, you can adjust the distance via the drawablePadding attribute.

So here's a screen of four TextViews in one LinearLayout:

And the full code (also in github):

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:orientation="vertical"
              android:layout_height="match_parent"
              android:divider="@drawable/divider_horizontal_dark"
              android:showDividers="middle">

    <TextView
        android:id="@+id/text1"
        android:drawableTop="@drawable/ic_notifications_black_24dp"
        android:drawableTint="@color/lemongrab"
        android:drawablePadding="8dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:padding="16dp"
        android:text="Text 1"/>

    <TextView
        android:id="@+id/text2"
        android:textSize="20sp"
        android:drawableRight="@drawable/ic_notifications_black_24dp"
        android:drawablePadding="8dp"
        android:padding="16dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Text 2"/>

    <TextView
        android:id="@+id/text3"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:drawableLeft="@drawable/ic_notifications_black_24dp"
        android:drawablePadding="8dp"
        android:padding="16dp"
        android:text="Text 3"
        android:textSize="20sp"/>


    <TextView
        android:id="@+id/text4"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:drawableLeft="@drawable/ic_notifications_black_24dp"
        android:drawablePadding="8dp"
        android:padding="16dp"
        android:text="Text 4"
        android:textSize="20sp" />


</LinearLayout>

If you need to update the Drawable tint at runtime (if you are basing it on some status field, for example), you can do so via code:

// left, top, right, and bottom
DrawableCompat.setTint(mText3.getCompoundDrawables()[0].mutate(), ContextCompat.getColor(this, R.color.red));

Note that we need to call mutate() or else the tint will be everywhere and it's gonna be a mess!

So there you have it! Remember kids, #perfmatters!