记录DataBinding使用-白红宇

记录DataBinding使用

阅读量：3748 次

发布时间：2019-05-22

本文共 10764 字，大约阅读时间需要 35 分钟。

例一

MainActivity

public class MainActivity extends AppCompatActivity {
       private ActivityMainBinding binding;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //会根据布局文件自动生成布局文件名开头的Binding类        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);        User user = new User(this,"Test", "User",true);        binding.setUser(user);    }}

User

public class User {
       public final String firstName;    public final String lastName;    public  Context context;    public boolean isFriend;    public User(Context context,String firstName, String lastName,boolean isFriend) {        this.context=context;        this.firstName = firstName;        this.lastName = lastName;        this.isFriend=isFriend;    }}

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这里写图片描述

例二绑定事件

MainActivity

public class MainActivity extends AppCompatActivity {
       private ActivityMainBinding binding;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //会根据布局文件自动生成布局文件名开头的Binding类        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);        User user = new User(this,"Test", "User",true);        binding.setUser(user);        binding.setHandlers(new MyHandlers());    }}

User类没变

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这里写图片描述

例三导入类

例四 List数组

MainActivity

public class MainActivity extends AppCompatActivity {
       private ActivityMainBinding binding;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //会根据布局文件自动生成布局文件名开头的Binding类        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);        List
   
     list=new ArrayList<>();        list.add("aaa");        binding.setUserList(list);    }}

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其中特别注意一点,在@{}表达式中不支持左括号,所以我们需要用转义字符代替左括号

例五静态

public class Teacher {    public static String   GG(){       return "1111111";    }}

例六变量

public class MainActivity extends AppCompatActivity {
       private ActivityMainBinding binding;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //会根据布局文件自动生成布局文件名开头的Binding类        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);        binding.setUserList("尼玛");    }}

和 Java 一样，java.lang.* 会被自动导入。

例七调用方法

public class User {    public final String firstName;    public final String lastName;    public List
   
     list=new ArrayList
    
     ();    public User(String firstName, String lastName) {        this.firstName = firstName;        this.lastName = lastName;    }    public  String  ggg(String st){        System.out.println("st = " + st);       return "asdas";    }}

public class MainActivity extends AppCompatActivity {
       private ActivityMainBinding binding;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //会根据布局文件自动生成布局文件名开头的Binding类        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);        binding.setUserList(new User("111","222"));    }}

例八 Context对象

public class MainActivity extends AppCompatActivity {
       private ActivityMainBinding binding;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //会根据布局文件自动生成布局文件名开头的Binding类        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);        binding.setUserList(new User("111","222"));    }}

public class User {
       public final String firstName;    public final String lastName;    public List
   
     list=new ArrayList
    
     ();    public User(String firstName, String lastName) {        this.firstName = firstName;        this.lastName = lastName;    }    public  String  ggg(Context context){        Toast.makeText(context,"toast",Toast.LENGTH_LONG).show();        return "asdas";    }}

binding 类会生成一个命名为context的特殊变量(其实就是 rootView 的 getContext())的返回值)，这个变量可用于表达式中. 如果有名为context的变量存在,那么生成的这个context特殊变量将被覆盖.

例九可以在表达式中直接引用带id的view,引用时采用驼峰命名法.

这里TextView直接引用第一次TextView，yaoyanName为id的驼峰命名

public class MainActivity extends AppCompatActivity {
       private ActivityMainBinding binding;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //会根据布局文件自动生成布局文件名开头的Binding类        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);        binding.setUserList(new User("111","222"));    }}

public class User {    public final String firstName;    public final String lastName;    public List
   
     list=new ArrayList
    
     ();    public User(String firstName, String lastName) {        this.firstName = firstName;        this.lastName = lastName;    }    public  String  ggg(String st){        System.out.println("st = " + st);        return "asdas";    }    public  String  ggg(Context context){        Toast.makeText(context,"toast",Toast.LENGTH_LONG).show();        return "asdas";    }}

例十 RecyclerView+DataBinding

MainActivity

public class MainActivity extends AppCompatActivity {
       private RecyclerView mRecyclerView;    private List
   
     mDatas;    private HomeAdapter mAdapter;    @Override    protected void onCreate(Bundle savedInstanceState)    {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initData();        mRecyclerView = (RecyclerView) findViewById(R.id.id_recyclerview);        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));        mRecyclerView.setAdapter(mAdapter = new HomeAdapter());    }    protected void initData()    {        mDatas = new ArrayList
    
     ();        for (int i = 1; i < 100; i++)        {            mDatas.add("----" + i);        }    }    class HomeAdapter extends RecyclerView.Adapter
     
          {
           @Override        public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType)        {            ViewDataBinding binding = DataBindingUtil.inflate(LayoutInflater.from(getApplicationContext()), R.layout.item_home, parent, false);            MyViewHolder holder=new MyViewHolder(binding);            return holder;        }        @Override        public void onBindViewHolder(MyViewHolder holder, int position)        {            ItemHomeBinding binding = (ItemHomeBinding) holder.getBinding();            String s = mDatas.get(position);            Item item=new Item();            item.setS(s);            binding.setVariable(BR.obj, item);            binding.executePendingBindings();        }        @Override        public int getItemCount()        {            return mDatas.size();        }        class MyViewHolder extends RecyclerView.ViewHolder        {
               private  ViewDataBinding binding;            public MyViewHolder(ViewDataBinding  binding)            {                super(binding.getRoot());                this.binding=binding;            }            public ViewDataBinding getBinding() {                return binding;            }        }    }}

executePendingBindings()方法.这个方法迫使数据立即绑定而不是在下一帧的时候才绑定.RecyclerView会在onBindViewHolder方法执行后立即测量这些view.假设没使用executePendingBindings()方法,由于在下一帧的时候才会绑定,view就会绑定错误的data,测量也会出错.因此,executePendingBindings()是很重要的.

Item

public class Item {    private String s;    public String getS() {        return s;    }    public void setS(String s) {        this.s = s;    }}

Item_XML

Main_XML

例十一自动设置属性

public class MainActivity extends AppCompatActivity {
       private RecyclerView mRecyclerView;    private List
   
     mDatas;    private HomeAdapter mAdapter;    private ActivityMainBinding activityMainBinding;    @Override    protected void onCreate(Bundle savedInstanceState)    {        super.onCreate(savedInstanceState);        activityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main);    }}

public class myView extends LinearLayout {
       public myView(Context context) {        super(context);    }    public myView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);    }    public myView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);    }    public myView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {        super(context, attrs, defStyleAttr, defStyleRes);    }    // 自动 Setter    public void setObject(String u) {        System.out.println("myView.setObject");    }}


   
       
            
     
                  app:object='@{"123"}'            android:layout_width="match_parent"            android:layout_height="match_parent" />

例十二 Observable

当表达式引用了一个类内的属性时，他会尝试直接调用域，getter，还有ObservableFields。

Observable 接口有一个添加/移除 listener 的机制，但通知取决于开发者。为了简化开发，我们创建了一个基类 BaseObservable，来实现 listener 注册机制。这个类也实现了域变动的通知，你只需要在 getter 上使用 Bindable 注解，并在 setter 中实现通知。

User

public class User  extends BaseObservable{
       public  String firstName;    public  String lastName;    public User(String firstName, String lastName) {        this.firstName = firstName;        this.lastName = lastName;    }    @Bindable    public String getFirstName() {        return this.firstName;    }    @Bindable    public String getLastName() {        return this.lastName;    }    public void setFirstName(String firstName) {        this.firstName = firstName;        notifyPropertyChanged(BR.firstName);    }    public void setLastName(String lastName) {        this.lastName = lastName;        notifyPropertyChanged(BR.lastName);    }}

MainActivity

public class MainActivity extends AppCompatActivity {
       private List
   
     mDatas;    private ActivityMainBinding activityMainBinding;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        activityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main);        User u=new User("123","456w");        activityMainBinding.setUser(u);    }}

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