Efficient Android Layouts (GOTO Conference)

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Efficient Android Layouts Dan Lew

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“Give me the place to stand, and I shall move the earth.” ~Archimedes

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“Give me a standing desk, and I shall write an Android app.” ~Me

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ViewGroups

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RelativeLayout ConstraintLayout LinearLayout FrameLayout Complex Simple

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RelativeLayout / ConstraintLayout • Position views relative to each other • RelativeLayout: Slow • ConstraintLayout: Alpha

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LinearLayout • Stack views vertically/horizontally • Weight distribution

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But I <3 RelativeLayout • LinearLayout == sometimes slow • RelativeLayout == always slow • ConstraintLayout == savior • Proﬁle!

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FrameLayout • Positioning based on parent bounds • Overlapping Views • Clickable item backgrounds • Toggle container

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public class AvatarView extends FrameLayout {    ImageView icon;  TextView initials;    public AvatarView(Context context, AttributeSet attrs) {  super(context, attrs);    LayoutInflater.from(context).inflate(R.layout.view_avatar, this);    icon = (ImageView) findViewById(R.id.icon);  initials = (TextView) findViewById(R.id.initials);  }    public void bind(Member member) {  // ...Load icon into ImageView...  // OR  // ...Setup initials in TextView...  }  }

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AvatarView (FrameLayout) FrameLayout ImageView TextView

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public class AvatarView extends FrameLayout {    ImageView icon;  TextView initials;    public AvatarView(Context context, AttributeSet attrs) {  super(context, attrs);    LayoutInflater.from(context).inflate(R.layout.view_avatar, this);    icon = (TextView) findViewById(R.id.icon);  initials = (TextView) findViewById(R.id.initials);  }    public void bind(Member member) {  // ...Load icon into ImageView...  // OR  // ...Setup initials in TextView...  }  }

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AvatarView (Framelayout) ImageView TextView

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Custom Drawing

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Step #1: onMeasure() (…sometimes you can skip this…)

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onMeasure() • onMeasure() signature void onMeasure(int widthMeasureSpec, int heightMeasureSpec) • measureSpec - packed integer int widthMode = MeasureSpec.getMode(widthMeasureSpec); int widthSize = MeasureSpec.getSize(widthMeasureSpec); int heightMode = MeasureSpec.getMode(heightMeasureSpec); int heightSize = MeasureSpec.getSize(heightMeasureSpec);

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MeasureSpec • EXACTLY - Must be that size • AT_MOST - Maximum width • UNDEFINED - Ideal width

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onMeasure() protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { int widthMode = MeasureSpec.getMode(widthMeasureSpec); int widthSize = MeasureSpec.getSize(widthMeasureSpec); int width; if (widthMode == MeasureSpec.EXACTLY) { width = widthSize; } else { int desiredWidth = 500; // Whatever calculation you want if (widthMode == MeasureSpec.AT_MOST) { width = Math.min(desiredWidth, widthSize); } else { width = desiredWidth; } } // ...to be continued... }

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onMeasure() @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { int width; int height; // ...Calculate width and height... setMeasuredDimension(width, height); }

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Step #2: onDraw() (this is up to you)

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Custom Drawables • onMeasure() -> getIntrinsicHeight() / getIntrinsicWidth() • onDraw() -> draw() • https://speakerdeck.com/cyrilmottier/mastering-android-drawables

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Styles

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Styles • No style • Style     <item name="android:background">#FF0000</item> 

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Efﬁcient • Semantically identical Views • All styled Views should change at once

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Not Efﬁcient • Single-use styles • Coincidentally using the same attributes    

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Not Efﬁcient • Single-use styles • Coincidentally using the same attributes    

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Not Efﬁcient • Single-use styles • Coincidentally using the same attributes    

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static final int NUM_COLUMNS = 3;    static final int NUM_RETRIES = 3; static final int NUM_THREE = 3;

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// static final int NUM_COLUMNS = 3;    // static final int NUM_RETRIES = 3;  static final int NUM_THREE = 3;

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Themes

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Themes • Affect multiple Views at once • Default styles • Conﬁgure system-created Views

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• Application • Activity • View

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AppCompat • Material on all devices • Baseline themes/styles • Enables View theming pre-Lollipop

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  <item name="buttonStyle">@style/MyButton</item>  <item name="android:spinnerItemStyle">@style/MySpinnerItem</item>    <item name="android:textAppearance">@style/MyText</item>  <item name="android:textAppearanceInverse">@style/MyTextInverse</item> 

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  <item name="selectableItemBackground">@drawable/bg</item>   

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Resources

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v24 port xxxhdpi w411dp h731dp en_US

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Resource Qualifier System • Define alternative resources for device configurations • Android automatically picks correct resource

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values-sw600dp-port values-port values-sw600dp values not sw600dp or portrait not sw600dp not portrait

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Resources as code • Resource == parameter • Parameter <-- device conﬁguration

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int square() {  return 8 * 8;  }  int squareLarge() {  return 16 * 16;  } int square(int num) {  return num * num;  } VS

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getResources().getBoolean(R.bool.is_portrait) false true

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setContentView(R.layout.activity_main)

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24sp 16sp

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  <item name="android:textSize">@dimen/welcome_text_size</item>  <item name="android:textColor">#FF00FF</item>  24sp 16sp

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activity_main.xml TextView style=@style/WelcomeText some_include.xml some_include.xml portrait default textSize=16sp textSize=24sp sw600dp default

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Drawables

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Image: https://www.ﬂickr.com/photos/ufv/8042499199 Design “I need this”

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Design “Not enough” “I tweaked the color,  here’s those assets again.”

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Assets as code

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Drawable XML • Built into Android • Simple shapes • State selectors • Layer lists

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Button Outline                  

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Button Selector                                      

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                        Button Selector (v21)

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Button Versions button_welcome_outline.xml button_welcome.xml button_welcome.xml (with ripple)

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Vector drawables

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VectorDrawable != SVG Design :(

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SVG -> VectorDrawable • Android Studio: New Vector Asset • Victor: github.com/trello/victor android {  sourceSets {  main {  svg.srcDir 'src/main/svg'  }  }  }

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Tinting Images • XML • Simple drawable.setColorFilter(color, PorterDuff.Mode.SRC_IN); • Comprehensive Drawable wrappedDrawable = DrawableCompat.wrap(drawable);  DrawableCompat.setTint(wrappedDrawable, color); Not backwards compatible

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Thank You! • @danlew42 • danlew.net • speakerdeck.com/dlew