Question

android library中怎样使用butterknife

Answer 1

配置:
用gradle配置的时候加入:
compile 'com.jakewharton:butterknife:6.1.0'

注意是加在Module: app的gradle文件中.
加上之后不用运行什么命令,直接Sync一下就可以在External Libraries里面看到butterknife.

功能1: 再也不用写findViewById()啦.
以前的:
mTextView1 = (TextView) findViewById(R.id.butter_text_view_1);

现在可以这样实现:
首先在变量声明的时候加上注解:
@InjectView(R.id.butter_text_view_2)
TextView mTextView2;

如果id找不到,会在编译的时候报错.

之后在设置好布局之后调用ButterKnife.inject():

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.demo_butter_knife);

//using butter knife
ButterKnife.inject(this);
}

之后View对象就可以直接使用了.

需要注意的是View变量声明的时候不能为private或者static.
除了Activity之外,你可以提供其他的View Root,来获取对象(执行注入).
还可以用来简化Adapter里面的ViewHolder:

ButterKnife in Fragment
在Fragment中也可以使用ButterKnife来获取View:

public class SimpleFragment extends Fragment {

@InjectView(R.id.fragment_text_view)
TextView mTextView;

public SimpleFragment() {
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_simple, container, false);
ButterKnife.inject(this, view);
mTextView.setText("TextView in Fragment are found!");
return view;
}
}

ButterKnife in Adapter ViewHolder
Adapter有一种常用的优化策略,就是使用ViewHolder来减少findViewById()的重复调用.
以前写过相关的博文: http://www.cnblogs.com/mengdd/p/3254323.html

用了ButterKnife之后, ViewHolder的使用可以变成这样:

@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = mInflater.inflate(R.layout.person_item_layout, null);
holder = new ViewHolder(convertView);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
Person person = getItem(position);
if (null != person) {
holder.name.setText(person.getName());
holder.age.setText(String.valueOf(person.getAge()));
holder.location.setText(person.getLocation());
holder.work.setText(person.getWork());
}

return convertView;
}

static class ViewHolder {
@InjectView(R.id.person_name)
TextView name;
@InjectView(R.id.person_age)
TextView age;
@InjectView(R.id.person_location)
TextView location;
@InjectView(R.id.person_work)
TextView work;

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

可以看到ViewHolder类加了一个带参数View的构造方法,用注解标记每个字段,再也不需要在getView()方法里调用findViewById()方法了.