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

支持 Activity 中的 View 注入

支持 View 中的 View 注入

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);