Android中ButterKnife框架

Android中ButterKnife框架

Android中ButterKnife框架

前言：發現一個不錯的注入框架，為了偷懶，還是拿來用了，其實我不是一個喜歡偷懶的碼農，但 … …

 

Introduction

Annotate fields with @Bind and a view ID for Butter Knife to find and automatically cast the corresponding view in your layout.

class ExampleActivity extends Activity {
  @Bind(R.id.title) TextView title;
  @Bind(R.id.subtitle) TextView subtitle;
  @Bind(R.id.footer) TextView footer;

  @Override public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.simple_activity);
    ButterKnife.bind(this);
    // TODO Use fields...
  }
}

Instead of slow reflection, code is generated to perform the view look-ups. Calling bind delegates to this generated code that you can see and debug.

The generated code for the above example is roughly equivalent to the following:

public void bind(ExampleActivity activity) {
  activity.subtitle = (android.widget.TextView) activity.findViewById(2130968578);
  activity.footer = (android.widget.TextView) activity.findViewById(2130968579);
  activity.title = (android.widget.TextView) activity.findViewById(2130968577);
}

RESOURCE BINDING

Bind pre-defined resources with @BindBool, @BindColor, @BindDimen, @BindDrawable, @BindInt,@BindString, which binds an R.bool ID (or your specified type) to its corresponding field.

class ExampleActivity extends Activity {
  @BindString(R.string.title) String title;
  @BindDrawable(R.drawable.graphic) Drawable graphic;
  @BindColor(R.color.red) int red; // int or ColorStateList field
  @BindDimen(R.dimen.spacer) Float spacer; // int (for pixel size) or float (for exact value) field
  // ...
}

NON-ACTIVITY BINDING

You can also perform binding on arbitrary objects by supplying your own view root.

public class FancyFragment extends Fragment {
  @Bind(R.id.button1) Button button1;
  @Bind(R.id.button2) Button button2;

  @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fancy_fragment, container, false);
    ButterKnife.bind(this, view);
    // TODO Use fields...
    return view;
  }
}

Another use is simplifying the view holder pattern inside of a list adapter.

public class MyAdapter extends BaseAdapter {
  @Override public View getView(int position, View view, ViewGroup parent) {
    ViewHolder holder;
    if (view != null) {
      holder = (ViewHolder) view.getTag();
    } else {
      view = inflater.inflate(R.layout.whatever, parent, false);
      holder = new ViewHolder(view);
      view.setTag(holder);
    }

    holder.name.setText(John Doe);
    // etc...

    return view;
  }

  static class ViewHolder {
    @Bind(R.id.title) TextView name;
    @Bind(R.id.job_title) TextView jobTitle;

    public ViewHolder(View view) {
      ButterKnife.bind(this, view);
    }
  }
}

You can see this implementation in action in the provided sample.

Calls to ButterKnife.bind can be made anywhere you would otherwise put findViewById calls.

Other provided binding APIs:

• Bind arbitrary objects using an activity as the view root. If you use a pattern like MVC you can bind the controller using its activity with ButterKnife.bind(this, activity).
• Bind a view's children into fields using ButterKnife.bind(this). If you use tags in a layout and inflate in a custom view constructor you can call this immediately after. Alternatively, custom view types inflated from XML can use it in the onFinishInflate()callback.

  VIEW LISTS

  You can group multiple views into a List or array.

  @Bind({ R.id.first_name, R.id.middle_name, R.id.last_name })
  List nameViews;

  The apply method allows you to act on all the views in a list at once.

  ButterKnife.apply(nameViews, DISABLE);
  ButterKnife.apply(nameViews, ENABLED, false);

  Action and Setter interfaces allow specifying simple behavior.

  static final ButterKnife.Action DISABLE = new ButterKnife.Action() {
    @Override public void apply(View view, int index) {
      view.setEnabled(false);
    }
  };
  static final ButterKnife.Setter ENABLED = new ButterKnife.Setter() {
    @Override public void set(View view, Boolean value, int index) {
      view.setEnabled(value);
    }
  };

  An Android Property can also be used with the apply method.

  ButterKnife.apply(nameViews, View.ALPHA, 0.0f);

  LISTENER BINDING

  Listeners can also automatically be configured onto methods.

  @OnClick(R.id.submit)
  public void submit(View view) {
    // TODO submit data to server...
  }

  All arguments to the listener method are optional.

  @OnClick(R.id.submit)
  public void submit() {
    // TODO submit data to server...
  }

  Define a specific type and it will automatically be cast.

  @OnClick(R.id.submit)
  public void sayHi(Button button) {
    button.setText(Hello!);
  }

  Specify multiple IDs in a single binding for common event handling.

  @OnClick({ R.id.door1, R.id.door2, R.id.door3 })
  public void pickDoor(DoorView door) {
    if (door.hasPrizeBehind()) {
      Toast.makeText(this, You win!, LENGTH_SHORT).show();
    } else {
      Toast.makeText(this, Try again, LENGTH_SHORT).show();
    }
  }

  Custom views can bind to their own listeners by not specifying an ID.

  public class FancyButton extends Button {
    @OnClick
    public void onClick() {
      // TODO do something!
    }
  }

  BINDING RESET

  Fragments have a different view lifecycle than activities. When binding a fragment inonCreateView, set the views to null in onDestroyView. Butter Knife has an unbind method to do this automatically.

  public class FancyFragment extends Fragment {
    @Bind(R.id.button1) Button button1;
    @Bind(R.id.button2) Button button2;
  
    @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
      View view = inflater.inflate(R.layout.fancy_fragment, container, false);
      ButterKnife.bind(this, view);
      // TODO Use fields...
      return view;
    }
  
    @Override public void onDestroyView() {
      super.onDestroyView();
      ButterKnife.unbind(this);
    }
  }

  OPTIONAL BINDINGS

  By default, both @Bind and listener bindings are required. An exception will be thrown if the target view cannot be found.

  To suppress this behavior and create an optional binding, add a @Nullable annotation to the field or method.

  Note: Any annotation named @Nullable can be used for this purpose. It is encouraged to use the@Nullable annotation from Android's support-annotations library, see Android Tools Project.

  @Nullable @Bind(R.id.might_not_be_there) TextView mightNotBeThere;
  
  @Nullable @OnClick(R.id.maybe_missing) void onMaybeMissingClicked() {
    // TODO ...
  }

  MULTI-METHOD LISTENERS

  Method annotations whose corresponding listener has multiple callbacks can be used to bind to any one of them. Each annotation has a default callback that it binds to. Specify an alternate using the callback parameter.

  @OnItemSelected(R.id.list_view)
  void onItemSelected(int position) {
    // TODO ...
  }
  
  @OnItemSelected(value = R.id.maybe_missing, callback = NOTHING_SELECTED)
  void onNothingSelected() {
    // TODO ...
  }

  BONUS

  Also included are findById methods which simplify code that still has to find views on a View,Activity, or Dialog. It uses generics to infer the return type and automatically performs the cast.

  View view = LayoutInflater.from(context).inflate(R.layout.thing, null);
  TextView firstName = ButterKnife.findById(view, R.id.first_name);
  TextView lastName = ButterKnife.findById(view, R.id.last_name);
  ImageView photo = ButterKnife.findById(view, R.id.photo);

  Add a static import for ButterKnife.findById and enjoy even more fun.

  Download

  Butter Knife v7.0.1 JAR

  The source code to the library and sample application as well as this website is available on GitHub. The Javadoc is also available to browse.

  MAVEN

  If you are using Maven for compilation you can declare the library as a dependency.

  
    com.jakewharton
    butterknife
    7.0.1
  

  GRADLE

  compile 'com.jakewharton:butterknife:7.0.1'

  Be sure to suppress this lint warning in your build.gradle.

  lintOptions {
    disable 'InvalidPackage'
  }

  Some configurations may also require additional exclusions.

  packagingOptions {
    exclude 'META-INF/services/javax.annotation.processing.Processor'
  }

  IDE CONFIGURATION

  Some IDEs require additional configuration in order to enable annotation processing.

  • IntelliJ IDEA — If your project uses an external configuration (like a Maven pom.xml) then annotation processing should just work. If not, try manual configuration.
  • Eclipse — Set up manual configuration.

    PROGUARD

    Butter Knife generates and uses classes dynamically which means that static analysis tools like ProGuard may think they are unused. In order to prevent them from being removed, explicitly mark them to be kept. To prevent ProGuard renaming classes that use @Bind on a member field thekeepclasseswithmembernames option is used.

    -keep class butterknife.** { *; }
    -dontwarn butterknife.internal.**
    -keep class **$$ViewBinder { *; }
    
    -keepclasseswithmembernames class * {
        @butterknife.* ;
    }
    
    -keepclasseswithmembernames class * {
        @butterknife.* ;
    }