注解

Posted 2023-03-01 xiong_hui_hui

定义注解

//定义注解类型：类，属性，方法
@Target(ElementType.FIELD)
//注解可见时候，一般运行时可见
@Retention(RetentionPolicy.RUNTIME)
public @interface Id 

使用注解

public class Bean 
    @Id
    private int id;
    public int getId()        return id;   
    public void setId(int id)    this.id = id;  
   

注解定位和反射取值

public class Use
  public int a;
  public void setA(Bean bean)
  Class clazz = bean.getClass();
  Field[] fields = clazz.getDeclaredFields();
            for (Field field:fields)
                if (field.getAnnotation(Id.class) != null)
                    field.setAccessible(true);
                    a = field.getInt(bean);
                
            

ButterKnife

1.配置：

compile ‘com.jakewharton:butterknife:6.1.0’

2.绑定事件：

activity：

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

fragment：

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) 
        View view = inflater.inflate(R.layout.fragment_simple, container, false);
        ButterKnife.inject(this, view);
        return view;
    

这个必须记得在onDestroyView中重置一下ButterKnife.reset(this);

viewHolder：

 public static class ViewHolder 
 public ViewHolder(View view) 
            ButterKnife.inject(this, view);
        
@InjectView(R.id.person_name) TextView name; @InjectView(R.id.person_age) TextView age; 

3.功能：

1. 不用写findViewById
   id找不到时会在编译时报错，view变量声明不能为private，static

  @InjectView(R.id.butter_text_view_2) 
  TextView mTextView2;

1. 不用写setOnClickListener
   还有ListView的@OnItemClick, CheckBox的@OnCheckedChanged等；
   方法不能为private，static；
   可绑定多个id;所以Listener参数都是optional，可写可不写；

@OnClick(R.id.button，R.id.button2)
    void finishA(View view) 
        finish();
    

1. 组建View List
   可同时获取多个view放入list

@InjectViews(R.id.first_name, R.id.middle_name, R.id.last_name)
List nameViews; 

4.apply()方法(要用再说)

共有3种形式:即Action, Setter和Property三种