2.5 Repository
没有过多需要描述的, 唯一需要区别的是返回值采用LiveData的方式, Demo 案例 来自google
class UserRepository {
private val webservice: Webservice = TODO()
// ...
fun getUser(userId: String): LiveData<User> {
// This isn't an optimal implementation. We'll fix it later.
val data = MutableLiveData<User>()
webservice.getUser(userId).enqueue(object : Callback<User> {
override fun onResponse(call: Call<User>, response: Response<User>) {
data.value = response.body()
}
// Error case is left out for brevity.
override fun onFailure(call: Call<User>, t: Throwable) {
TODO()
}
})
return data
}
}
final-architecture.png
根据此图, Repository的部分, 因为涉及到可能来自本地的数据源,或者来自网络的数据源,甚至会存在不同的数据有逻辑顺序的数据源,例如,先获取本地数据,在本地获取成功后,再次获取到远端的数据, 因而数据层,负责这些部分.
2.6 DataBinding
Google 官方说明: Data Binding Library
DataBinding Communication
DataBinding Communication.png
DataBinding Init Sequence
DataBinding Init Sequence.png
DataBindingUtil.sMapper的实现
/**
* Inflates a binding layout and returns the newly-created binding for that layout.
* This uses the DataBindingComponent set in
* {@link #setDefaultComponent(DataBindingComponent)}.
* <p>
* Use this version only if <code>layoutId</code> is unknown in advance. Otherwise, use
* the generated Binding's inflate method to ensure type-safe inflation.
*
* @param <T> Type of the generated binding class.
* @param inflater The LayoutInflater used to inflate the binding layout.
* @param layoutId The layout resource ID of the layout to inflate.
* @param parent Optional view to be the parent of the generated hierarchy
* (if attachToParent is true), or else simply an object that provides
* a set of LayoutParams values for root of the returned hierarchy
* (if attachToParent is false.)
* @param attachToParent Whether the inflated hierarchy should be attached to the
* parent parameter. If false, parent is only used to create
* the correct subclass of LayoutParams for the root view in the XML.
* @return The newly-created binding for the inflated layout or <code>null</code> if
* the layoutId wasn't for a binding layout.
* @throws InflateException When a merge layout was used and attachToParent was false.
* @see #setDefaultComponent(DataBindingComponent)
*/
// @Nullable don't annotate with Nullable. It is unlikely to be null and makes using it from
// kotlin really ugly. We cannot make it NonNull w/o breaking backward compatibility.
public static <T extends ViewDataBinding> T inflate(@NonNull LayoutInflater inflater,
int layoutId, @Nullable ViewGroup parent, boolean attachToParent) {
return inflate(inflater, layoutId, parent, attachToParent, sDefaultComponent);
}
/**
* Inflates a binding layout and returns the newly-created binding for that layout.
* <p>
* Use this version only if <code>layoutId</code> is unknown in advance. Otherwise, use
* the generated Binding's inflate method to ensure type-safe inflation.
*
* @param <T> Type of the generated binding class.
* @param inflater The LayoutInflater used to inflate the binding layout.
* @param layoutId The layout resource ID of the layout to inflate.
* @param parent Optional view to be the parent of the generated hierarchy
* (if attachToParent is true), or else simply an object that provides
* a set of LayoutParams values for root of the returned hierarchy
* (if attachToParent is false.)
* @param attachToParent Whether the inflated hierarchy should be attached to the
* parent parameter. If false, parent is only used to create
* the correct subclass of LayoutParams for the root view in the XML.
* @param bindingComponent The DataBindingComponent to use in the binding.
* @return The newly-created binding for the inflated layout or <code>null</code> if
* the layoutId wasn't for a binding layout.
* @throws InflateException When a merge layout was used and attachToParent was false.
*/
// @Nullable don't annotate with Nullable. It is unlikely to be null and makes using it from
// kotlin really ugly. We cannot make it NonNull w/o breaking backward compatibility.
public static <T extends ViewDataBinding> T inflate(
@NonNull LayoutInflater inflater, int layoutId, @Nullable ViewGroup parent,
boolean attachToParent, @Nullable DataBindingComponent bindingComponent) {
final boolean useChildren = parent != null && attachToParent;
final int startChildren = useChildren ? parent.getChildCount() : 0;
final View view = inflater.inflate(layoutId, parent, attachToParent);
if (useChildren) {
return bindToAddedViews(bindingComponent, parent, startChildren, layoutId);
} else {
return bind(bindingComponent, view, layoutId);
}
}
static <T extends ViewDataBinding> T bind(DataBindingComponent bindingComponent, View root,
int layoutId) {
return (T) sMapper.getDataBinder(bindingComponent, root, layoutId);
}
在Fragment中,采用inflate的方式时, 我们看到最终是需要通过变量sMapper来寻找到的, 而sMapper的实例是: DataBinderMapperImpl, 这块在源码中我们没有看到, 实现在哪里? 其实是我们在开启了
dataBinding {
enabled = true
}
时, 代码会自动生成,
在我们的application的工程(一般名字为app)中查找实现部分
package android.databinding;
public class DataBinderMapperImpl extends MergedDataBinderMapper {
DataBinderMapperImpl() {
addMapper(new com.test.app.DataBinderMapperImpl());// 将我们的application的DataBinderMapperImpl 注册
}
}
继续查看实现的com.test.app.DataBinderMapperImpl的实现
package com.test.app;
public class DataBinderMapperImpl extends DataBinderMapper {
private static final SparseIntArray INTERNAL_LAYOUT_ID_LOOKUP = new SparseIntArray(0);
static {
}
@Override
public ViewDataBinding getDataBinder(DataBindingComponent component, View view, int layoutId) {
int localizedLayoutId = INTERNAL_LAYOUT_ID_LOOKUP.get(layoutId);
if(localizedLayoutId > 0) {
final Object tag = view.getTag();
if(tag == null) {
throw new RuntimeException("view must have a tag");
}
}
return null;
}
@Override
public ViewDataBinding getDataBinder(DataBindingComponent component, View[] views, int layoutId) {
if(views == null || views.length == 0) {
return null;
}
int localizedLayoutId = INTERNAL_LAYOUT_ID_LOOKUP.get(layoutId);
if(localizedLayoutId > 0) {
final Object tag = views[0].getTag();
if(tag == null) {
throw new RuntimeException("view must have a tag");
}
switch(localizedLayoutId) {
}
}
return null;
}
@Override
public int getLayoutId(String tag) {
if (tag == null) {
return 0;
}
Integer tmpVal = InnerLayoutIdLookup.sKeys.get(tag);
return tmpVal == null ? 0 : tmpVal;
}
@Override
public String convertBrIdToString(int localId) {
String tmpVal = InnerBrLookup.sKeys.get(localId);
return tmpVal;
}
@Override
public List<DataBinderMapper> collectDependencies() {
ArrayList<DataBinderMapper> result = new ArrayList<DataBinderMapper>(1);
result.add(new com.test.module.DataBinderMapperImpl());// 将Application的依赖的module注册进来
return result;
}
private static class InnerBrLookup {
static final SparseArray<String> sKeys = new SparseArray<String>(14);
static {
sKeys.put(0, "_all");
sKeys.put(1, "image");
sKeys.put(2, "item");
sKeys.put(3, "onClick");
sKeys.put(4, "data");
sKeys.put(5, "visibility");
sKeys.put(6, "vm");
sKeys.put(7, "text");
sKeys.put(8, "stepVm");
sKeys.put(9, "type");
sKeys.put(10, "retry");
sKeys.put(11, "refundOnly");
sKeys.put(12, "refundAndReturn");
}
}
private static class InnerLayoutIdLookup {
static final HashMap<String, Integer> sKeys = new HashMap<String, Integer>(0);
static {
}
}
}
通过上述的代码的分析得知,
- DataBindingUtil.sMapper的具体的实现,是通过代码生成器生成的
- 此mapper是在application的工程中,生成的类
- 此类,一般会有一个注册的mapper,为当前application的mapper
- application的mapper中,注册了其关联工程的mapper(这也是为什么, 我们的build.gradle中的dataBinding的enabled = true, 要从依赖的源头到application的工程一路注册,因为mapper,也是逐级传递的)
- 每个开启了dataBinding的enable=true的模块都有自己的DataBinderMapperImpl, 负责的是自己模块的dataBinding的处理和负责搜集子模块的DataBinderMapperImpl
- 通过这一系列的DataBinderMapperImpl, 在调用 DataBindUtils的方法
static <T extends ViewDataBinding> T bind(DataBindingComponent bindingComponent, View root,
int layoutId) {
return (T) sMapper.getDataBinder(bindingComponent, root, layoutId);
}
便可以找到对应的ViewDataBinding,并且初始化.
