ButterKnife使用详解

ButterKnife 优势：
1.强大的View绑定和Click事件处理功能，简化代码，提升开发效率
2.方便的处理Adapter里的ViewHolder绑定问题
3.运行时不会影响APP效率，使用配置方便
4.代码清晰，可读性强

使用心得：
1.Activity ButterKnife.bind(this);必须在setContentView();之后，且父类bind绑定后，子类不需要再bind
2.Fragment ButterKnife.bind(this, mRootView);
3.属性布局不能用private or static 修饰，否则会报错
4.setContentView()不能通过注解实现。（其他的有些注解框架可以）

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本篇详细讲述ButterKnife的使用
项目添加ButterKnife移步：http://blog.csdn.net/skeeing/article/details/52384025

1 . View视图的绑定

class ExampleActivity extends Activity {
  @BindView(R.id.title) TextView title;
  @BindView(R.id.subtitle) TextView subtitle;
  @BindView(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...
  }
}

2 . 多种资源id的绑定

@BindBool, @BindColor, @BindDimen, @BindDrawable, @BindInt, @BindString

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
  // ...
}

3 . 非Activity的View绑定

通过提供视图根元素，你可以执行绑定任意对象

public class FancyFragment extends Fragment {
  @BindView(R.id.button1) Button button1;
  @BindView(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;
  }
}

View Holder中简化视图的用法

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 {
    @BindView(R.id.title) TextView name;
    @BindView(R.id.job_title) TextView jobTitle;

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

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

4 . View集合绑定

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

提供自定义行为的两个接口

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);
  }
};

属性配置文件也支持被设定

ButterKnife.apply(nameViews, View.ALPHA, 0.0f);//设置集合里所有元素透明

5 . 事件绑定

@OnClick(R.id.submit)
public void submit(View view) {
  // TODO submit data to server...
}
@OnClick(R.id.submit)
public void sayHi(Button button) {
  button.setText("Hello!");
}

指定多个控件绑定一个方法

@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.
自定义view可以绑定在他们自己的监听器上并且不需要具体声明一个ID。
public class FancyButton extends Button {
  @OnClick
  public void onClick() {
    // TODO do something!
  }
}

6. 解除绑定

Fragment和Activity相比有不同的生命周期。当在一个Fragment的onCreateView中绑定的时候，需要在onDestoryView中设置Views为null。但是，Butter Knife 有一个 unbind 方法来自动的做这件事。

public class FancyFragment extends Fragment {
  @BindView(R.id.button1) Button button1;
  @BindView(R.id.button2) Button button2;
  private Unbinder unbinder;

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

  @Override public void onDestroyView() {
    super.onDestroyView();
    unbinder.unbind();
  }
}

7 . 可选注解

“绑定”和“监听”绑定都是必需的。如果不能找到目标视图，则将抛出异常。所以做空处理
IllegalStateException转为NullPointerException，可以作捕获操作

@Nullable @BindView(R.id.might_not_be_there) TextView mightNotBeThere;

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

8 . 多种监听器

@OnItemSelected(R.id.list_view)
void onItemSelected(int position) {
  // TODO ...
}

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

9 . 其它

一些增强的方法，不需要强转类型

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);