原文链接:http://stormzhang.com/openandroid/android/2014/01/12/android-butterknife/
俗话说:“不会偷懒的程序员不是好的程序员!”。作为一名Android开发,是不是经常厌烦了大量的findViewById以及setOnClickListener代码,而ButterKnife是一个专注于Android系统的View注入框架,让你从此从这些烦人臃肿的代码中解脱出来。先来看一段代码示例说明下ButterKnife是如何简化代码的:
注意:如果你是使用的Eclipse引用该library,你需要参考这里Eclipse Configuration做一些配置,否则会运行出错。
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...
}
}
而用ButterKnife之后的代码是这样的:
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。
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:
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...
}
}
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;
}
}
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);
}
}
}
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();
}
}
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);
最后,如果你是用Android Studio来作为IDE的话,那么有一个ButterKnife的插件android-butterknife-zelezny, 该插件可以让你手动生成上述注入代码,从此让自己成为一个更懒惰的程序员。