关于开源项目ButterKnife的使用心得

开源项目地址：https://github.com/JakeWharton/butterknife

个人使用总结：

本人用的是ADT，直接导入jar包使用是会报错的，注解无效。解决办法是选中项目右键properties->Java Compiler->Annotation Processin(选中Enable project specific setting)->展开后选中Factory path选中Enable project specific setting添加butterknife的jar包进来

有一些小伙伴说找不到Java Compiler中的Annotation Processin是因为没有安装插件，插件地址：http://download.eclipse.org/releases/juno，然后选择Programming Languages->Eclipse Java Development Tools后安装完成重启即可正常运行

展示一下使用效果：(以下转载自stormzhang前辈的博客，http://stormzhang.com/openandroid/android/2014/01/12/android-butterknife/)

使用前：

class ExampleActivity extends Activity {
  TextView title;
  TextView subtitle;
  TextView footer;

  @Override public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.simple_activity);
    title = (TextView) findViewById(R.id.title);
    subtitle = (TextView) findViewById(R.id.subtitle);
    footer = (TextView) findViewById(R.id.footer);

    // TODO Use views...
  }
}

使用后

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...
  }
}

是不是非常简洁易用？下面就来系统的介绍下ButterKnife的用法。

Butter Knife 的特性

1. 支持 Activity 中的 View 注入

2. 支持 View 中的 View 注入

3. 支持 View 事件回调函数注入

目前支持如下事件回调函数：

• View: @OnLongClick and @OnFocusChanged.

• TextView: @OnEditorAction.

• AdapterView: @OnItemClick and @OnItemLongClick.

• CompoundButton: @OnCheckedChanged.

下面来看一些注入的示例代码：

在Activity 中注入

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...
  }
}

在 Fragment 中注入

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;
  }
}

在 ViewHolder 模式中注入

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 convertView;
  }
 
  static class ViewHolder {
    @InjectView(R.id.title) TextView name;
    @InjectView(R.id.job_title) TextView jobTitle;
 
    public ViewHolder(View view) {
      ButterKnife.inject(this, view);
    }
  }
}

注入回调函数

下面是几种注入回调函数的方法示例:

// 带有 Button 参数
@OnClick(R.id.submit)
public void sayHi(Button button) {
  button.setText("Hello!");
}
 
// 不带参数
@OnClick(R.id.submit)
public void submit() {
  // TODO submit data to server...
}
 
// 同时注入多个 View 事件
@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();
  }
}

Reset函数

如果需要在 界面 销毁的时候，把注入的 View 设置为 Null， 则可以用 reset 函数：

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();
    Views.reset(this);
  }
}

另外 还支持 可选的 View 注入，如果该 View 没有，就没有吧：

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

还有两个 findViewById 函数来简化查找 View 的方式，如果上面都满足不了你的需求，你可以用用他们：

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