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[Deprecated]

View Binding does everything holdr does but is a first-party solution. I will still be maintaing this project and fixing any bugs, but I will not be adding any new features.

Holdr

What is Holdr?

Holdr generates classes based on your layouts to help you interact with them in a type-safe way. It removes the boilerplate of doing TextView myTextView = findViewById(R.id.my_text_view) all the time.

Doesn't Butter Knife/AndroidAnnotaions/RoboGuice already do that?

This is a different approach to solving the same problem, the important difference is your layout dictates what is generated instead of annotations on your classes. This means that it's much less likely for your code and layouts to get out of sync.

This approach also means zero reflection (and no proguard issues) and works equally as well in library projects.

Usage

Simply apply the gradle plugin and your done!

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.0.0'
        classpath 'me.tatarka.holdr:gradle-plugin:1.5.2'
    }
}

repositories {
    mavenCentral()
}

apply plugin: 'com.android.application'
apply plugin: 'me.tatarka.holdr'

alternativly, you can use the new gradle 2.1+ syntax

plugins {
  id "me.tatarka.holdr" version "1.5.2"
}

Say you have a layout file hand.xml.

<!-- hand.xml -->
<?xml version="1.0" encoding="utf-8"?>

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical" 
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        tools:text="Hello, Holdr!"/>
</LinearLayout>

Holdr will create a class for you named your.application.id.holdr.Holdr_Hand. This class is basically a view holder that you can instantiate anywhere you have a view.

In an Activity

public class MyActivity extends Activity {
    private Holdr_Hand holdr;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.hand);
        holdr = new Holdr_Hand(findViewById(android.R.id.content));
        holdr.text.setText("Hello, Holdr!");
    }
}

In a Fragment

public class MyFragment extends Fragment {
    private Holdr_Hand holdr;
    
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.hand, container, false);
    }
    
    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        holdr = new Holdr_Hand(view);
        holdr.text.setText("Hello, Holdr!");
    }
    
    @Override
    public void onDestroyView() {
        super.onDestroyView();
        holdr = null;
    }
}

In an Adapter

public class MyAdapter extends BaseAdapter {
    // other methods
    
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Holdr_Hand holdr;
        if (convertView == null) {
            holdr = new Holdr_Hand(inflater.inflate(R.layout.hand, parent, false));
            holdr.getView().setTag(holdr);
        } else {
            holdr = (Holdr_Hand) convertView.getTag();
        }
        holdr.text.setText(getItem(position));
        return holdr.getView();
    }
}

In a Custom View

public class MyCustomView extends LinearLayout {
    Holdr_Hand holdr;
    
    // other methods
    
    private void init() {
        holdr = new Holdr_Hand(inflate(getContext(), R.layout.hand, this));
        holdr.text.setText("Hello, Holdr!");
    }
}

Multiple layouts

You may have multiple instances of a layout (in layout and layout-land for example). In that case Holdr will merge the id's across them. If an id appears in one and not the other, a @Nullable annotation will be generated to warn you of this.

If the type of the view doesn't match, Holdr will take the most conservative route and use type View. If instead, they share a common superclass and you want to use that, you can use the app:holdr_class to override the view type so that they match.

<!-- layout/hand.xml -->
<TextView
    android:id="@+id/text"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    tools:text="Hello, Holdr!"/>

<!-- layout-land/hand.xml -->
<com.example.MyCustomTextView
    android:id="@+id/text"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    tools:text="Hello, Holdr!"
    app:holdr_class="TextView"/>

Callback Listeners

You can also specify listeners for your Activity/Fragment/Whatever to handle to make working with callbacks a bit nicer. For example, if you had the layout file hand.xml,

<!-- hand.xml -->
<?xml version="1.0" encoding="utf-8"?>

<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:orientation="vertical" 
  android:layout_width="match_parent"
  android:layout_height="match_parent">

  <Button
      android:id="@+id/my_button"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="Hello, Holdr!"
      app:holdr_onClick="true"/>
</LinearLayout>

The generated Holdr_Hand class will also have a listener interface for you to implement.

public class MyActivity extends Activity implements Holdr_Hand.Listener {
  private Holdr_Hand holdr;
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.hand);
      holdr = new Holdr_Hand(findViewById(android.R.id.content));
      holdr.setListener(this);
  }
  
  @Override
  public void onMyButtonClick(Button myButton) {
      // Handle button click.
  }
}

Here is a list of all the listeners you can handle:

  • holdr_onTouch
  • holdr_onClick
  • holdr_onLongClick
  • holdr_onFocusChange
  • holdr_onCheckedChanged
  • holdr_onEditorAction
  • holdr_onItemClick
  • holdr_onItemLongClick

You can also specify a custom method name by doing app:holdr_onClick="myCustomMethodName" instead. You can also specify the same name on multiple views and they will share a listener (provided the listeners are of the same type).

Custom Superclass

Want to use a Holdr in a place where you need a specific subclass? (RecyclerView.ViewHolder for example). Just use the attribute app:holdr_superclass="com.example.MySuperclass and it will subclass that instead of Holdr. The only requirement is that the superclass must contain a constructor that takes a View.

Controlling What's Generated

If you don't like the idea of a whole bunch of code being generated for all your layouts (It's really not much, I promise!), you can add holdr.defaultInclude false to your build.gradle and then you can manually opt-in for each of your layouts.

The easiest way to opt-in is to add app:holdr_include="all" to the root view of that layout.

By default, every view with an id gets added to the generated class. You can use the attributes holdr_include and holdr_ignore to get more granular control. Both take either the value "view" to act on just the view it's used on or "all" to act on that view and all it's children. For example,

<LinearLayout
 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:id="@+id/container"
 android:orientation="vertical"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 app:holdr_ignore="all">

 <TextView
     android:id="@+id/text1"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     tools:text="Hello, Holdr!"
     app:holdr_include="view"/>
 `   
 <TextView
     android:id="@+id/text2"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     tools:text="Hello, Holdr!"/>
</LinearLayout>

would include only text1 in the generated class.

Note: The current implementation only allows you to nest these attributes 2 levels deep (ignore inside include inside ignore won't work). I don't think there is a use case complex enough to warrant this, but it may be fixed in a later version if there is a need.

Finally, if you don't like the field name generated for a specific id, you can set it yourself by using app:holdr_field_name="myBetterFieldName" on a view.

Android Studio Plugin

Tired of having to build your project after every layout change? With the intellij plugin the Holdr classes will be auto-generated as soon as you save!

Go to Settings -> Plugins -> Browse Repositories... and search for "Holdr".

The plugin will also allow you to do a refactor-rename on holdr fields and use goto-source (Ctrl-click or Ctrl-B) to go directly to the view in the layout.

(Requires Android Studio 0.6.0+ or Intellij 14)

If instead you feel like living on the edge, you can build install the plugin manually.

  1. Clone the repo
  2. Change studio.path in gradle.properties to point to your Android Studio/Intellij instalation directory
  3. Run ./gradlew intellij-plugin:build --configure-on-demand
  4. Go to Settings -> Plugins -> Install plugin from disk... and install the jar in ./intellij-plugin/build/libs/