Butter Knife:一个安卓视图注入框架

Butter Knife:一个安卓视图注入框架

2014年5月8日 星期四

14:52

官网: http://jakewharton.github.io/butterknife/

GitHub地址: https://github.com/JakeWharton/butterknife

JavaDocs地址: http://jakewharton.github.io/butterknife/javadoc/

 注:本随笔翻译自官网,做了一些整理和注释。来自我的OneNote笔记

大纲:

  1. @InjectView (ActivityFragment)
  2. @InjectViews
  3. apply
  4. @OnClick
  5. reset
  6. @Optional
  7. @OnItemSelected
  1. TextView firstName = ButterKnife.findById(view, R.id.first_name);

 

 

 

 

Activity的注入方法:

//基本使用方法:在onCreate方法中调用ButterKnife.inject(this),然后就可以调用注解了

class ExampleActivity extends Activity {

  @InjectView(R.id.title) TextView title;

  @InjectView(R.id.subtitle) TextView subtitle;

  @InjectView(R.id.footer) TextView footer;

 

  @Override public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.simple_activity);

    ButterKnife.inject(this);

    // TODO Use "injected" views...

  }

}

这个注入不是通过反射实现了(反射比较慢),而是直接生成代码。上面的三个注入最后生成如下的代码

public void inject(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);

}

Fragment的注入方法

public class FancyFragment extends Fragment {

  @InjectView(R.id.button1) Button button1;

  @InjectView(R.id.button2) Button button2;

 

  @Override View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.fancy_fragment, container, false);

    //仅仅是这里的区别

    ButterKnife.inject(this, view);

    // TODO Use "injected" views...

    return view;

  }

}

简化ViewHolder的使用 

public class MyAdapter extends BaseAdapter {

  @Override public View getView(int position, View view, ViewGroup parent) {

    //ViewHolder是一个普通的类,这个类包含了一个Adapter需要的所有View,然后设置到了tag中,方便复用

    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 convertView;

  }

//这里是ViewHolder:可以这样进行注入

  static class ViewHolder {

    @InjectView(R.id.title) TextView name;

    @InjectView(R.id.job_title) TextView jobTitle;

 

    public ViewHolder(View view) {

      ButterKnife.inject(this, view);

    }

  }

}

注入一个View列表:@InjectViews

//注入一个View列表

@InjectViews({ R.id.first_name, R.id.middle_name, R.id.last_name })

List<EditText> nameViews;

//调用apply方法批量给View设置属性

ButterKnife.apply(nameViews, DISABLE);

ButterKnife.apply(nameViews, ENABLED, false);

//其中,DISABLE和ENABLED是两个接口的实现:Action,Setter

static final Action<View> DISABLE = new Action<>() {

  @Override public void apply(View view, int index) {

    view.setEnabled(false);

  }

}

static final Setter<View, Boolean> ENABLED = new Setter<>() {

  @Override public void set(View view, Boolean value, int index) {

    view.setEnabled(value);

  }

}

////View所有的属性都可以在apply方法中调用

ButterKnife.apply(nameViews, View.ALPHA, 0);

 

点击监听器的注入:OnClickListener -> @OnClick

//简单使用

@OnClick(R.id.submit)ren

public void submit() {

  // TODO submit data to server...

}

//你可以传入一个参数,Butter Knife会自动将注入的View转换为对应的类型

@OnClick(R.id.submit)

public void sayHi(Button button) {

  button.setText("Hello!");

}

//当然,也可以指定多个视图的IDs,用来进行通用的处理

@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();

  }

}

注入的重置:reset

Fragment中,我们需要在onDestroyView中设置这些Viewnull,但是只要调用reset方法,Butter Knife会自动执行这个步骤。

public class FancyFragment extends Fragment {

  @InjectView(R.id.button1) Button button1;

  @InjectView(R.id.button2) Button button2;

 

  @Override View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.fancy_fragment, container, false);

    ButterKnife.inject(this, view);

    // TODO Use "injected" views...

    return view;

  }

 

  @Override void onDestroyView() {

    super.onDestroyView();

    ButterKnife.reset(this);

  }

}

可选的注入 @Optional

默认情况下,@InjectView@OnClick注入是必须了,所以,如果找不到目标View就会抛出异常。如果想抑制这种情况,可以通过@Optional注解:

@Optional @InjectView(R.id.might_not_be_there) TextView mightNotBeThere;

 

@Optional @OnClick(R.id.maybe_missing) void onMaybeMissingClicked() {

  // TODO ...

}

多方法的监听@OnItemSelected

有些监听注解响应的方法有多个回调函数,所以,我们可以通过指定回调参数来实现多个回调方法的绑定。

@OnItemSelected(R.id.list_view)

void onItemSelected(int position) {

  // TODO ...

}

 

@OnItemSelected(value = R.id.maybe_missing, callback = NOTHING_SELECTED)

void onNothingSelected() {

  // TODO ...

}

BONUS:其实就是一个方便的静态方法而已

一般我们实例化一个View的时候是通过findById(id),然后强制转换实现的,这样的代码看着不雅观。所以,ButterKnife有一个方法自动帮我们进行这样的转换(Context可以为ViewActivity),如下面的例子:

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);

 

最新版本:5.0.1

 

 

集成方法

Maven

<dependency>

  <groupId>com.jakewharton</groupId>

  <artifactId>butterknife</artifactId>

  <version>5.0.1</version>

</dependency>

Gradle

  1. 添加依赖

compile 'com.jakewharton:butterknife:5.0.1'

  1. 消除lint warning

lintOptions {

  disable 'InvalidPackage'

}

  1. Some configurations may also require additional exclusions.

packagingOptions {

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

}

 

Procuard配置:(这个配置是为了打包apk的时候不至于把你的那些貌似没有用过的程序片段给删掉了)

-dontwarn butterknife.internal.**

-keep class **$$ViewInjector { *; }

-keepnames class * { @butterknife.InjectView *;}

 

posted @ 2014-07-29 00:43 天外的星星 阅读(...) 评论(...) 编辑 收藏