项目地址:https://github.com/googlesamples/android-architecture/tree/todo-mvp/
在第一篇说过,todo-mvp只是android-architecture项目的一个分支
todo-mvp主要使用了mvp架构来实现,如图
图中的Repository就是数据源,即M,包括Local数据和Remote数据;Fragment为V;Activity中依赖了P,V(Fragment)与P相互依赖,P依赖了M(Repository),即P分离了M与V;当然有时我们不需要Fragment,那么可以直接使用Activity来作为V
(不含测试package):
除BaseView、BasePresenter两个接口,其他package都以业务功能来划分的:
addedittask —— 添加任务
data —— 数据源
statistics —— 任务统计
taskdetail —— 任务详情
tasks —— 任务列表
util —— 工具类
BaseView、BasePresenter两个接口:
public interface BaseView {
void setPresenter(T presenter);
}
public interface BasePresenter {
void start();
}
Task —— 它就是一个java bean
TasksDataSource —— Task数据操作的接口
TasksRepository —— 实现了TasksDataSource,依赖了TasksLocalDataSource、TasksRemoteDataSource,实现根据不同情形,获取Local或Remote的相关数据
TasksRemoteDataSource —— 远程数据,一般可能走网络,当然这里没有,只是模拟
TasksPersistenceContract —— 约定了数据库表字段
TasksDbHelper —— 数据库操作
TasksLocalDataSource —— 本地数据源
注:项目中默认只操作了Local数据,若也想操作Remote,只需要将TasksRepository中的属性mCacheIsDirty=true,即可
接下来挑一个业务模块分析一下(其它模块大同小异),比如tasks
ScrollChildSwipeRefreshLayout —— 这是一个自定义Layout,不用理会
TasksActivity —— Activity
TasksContract —— 契约接口(每个功能模块都有一个),约定了两个子接口View和Presenter,及各自的公共方法;分别实现BaseView、BasePresenter两个接口
TasksFilterType —— enum类,任务过滤类型
TasksFragment —— Fragment,实现TasksContract.View
TasksPresenter —— Presenter,实现TasksContract.Presenter
再来分析一个具体的业务功能,比如展示tasks列表
在TasksContract#Presenter中,有一个方法:
void loadTasks(boolean forceUpdate);
相应的TasksContract#View中,有一个方法:
void showTasks(List<Task> tasks);
看下TasksPresenter的相关的一些代码:
public class TasksPresenter implements TasksContract.Presenter {
private final TasksRepository mTasksRepository;
private final TasksContract.View mTasksView;
private TasksFilterType mCurrentFiltering = TasksFilterType.ALL_TASKS;
private boolean mFirstLoad = true;
public TasksPresenter(@NonNull TasksRepository tasksRepository, @NonNull TasksContract.View tasksView) {
mTasksRepository = checkNotNull(tasksRepository, "tasksRepository cannot be null");
mTasksView = checkNotNull(tasksView, "tasksView cannot be null!");
mTasksView.setPresenter(this);
}
@Override
public void start() {
loadTasks(false);
}
@Override
public void loadTasks(boolean forceUpdate) {
// Simplification for sample: a network reload will be forced on first load.
loadTasks(forceUpdate || mFirstLoad, true);
mFirstLoad = false;
}
private void loadTasks(boolean forceUpdate, final boolean showLoadingUI) {
if (showLoadingUI) {
mTasksView.setLoadingIndicator(true);
}
if (forceUpdate) {
mTasksRepository.refreshTasks();
}
// The network request might be handled in a different thread so make sure Espresso knows
// that the app is busy until the response is handled.
EspressoIdlingResource.increment(); // App is busy until further notice
mTasksRepository.getTasks(new TasksDataSource.LoadTasksCallback() {
@Override
public void onTasksLoaded(List tasks) {
List tasksToShow = new ArrayList();
// This callback may be called twice, once for the cache and once for loading
// the data from the server API, so we check before decrementing, otherwise
// it throws "Counter has been corrupted!" exception.
if (!EspressoIdlingResource.getIdlingResource().isIdleNow()) {
EspressoIdlingResource.decrement(); // Set app as idle.
}
// We filter the tasks based on the requestType
for (Task task : tasks) {
switch (mCurrentFiltering) {
case ALL_TASKS:
tasksToShow.add(task);
break;
case ACTIVE_TASKS:
if (task.isActive()) {
tasksToShow.add(task);
}
break;
case COMPLETED_TASKS:
if (task.isCompleted()) {
tasksToShow.add(task);
}
break;
default:
tasksToShow.add(task);
break;
}
}
// The view may not be able to handle UI updates anymore
if (!mTasksView.isActive()) {
return;
}
if (showLoadingUI) {
mTasksView.setLoadingIndicator(false);
}
processTasks(tasksToShow);
}
@Override
public void onDataNotAvailable() {
// The view may not be able to handle UI updates anymore
if (!mTasksView.isActive()) {
return;
}
mTasksView.showLoadingTasksError();
}
});
}
private void processTasks(List tasks) {
if (tasks.isEmpty()) {
// Show a message indicating there are no tasks for that filter type.
processEmptyTasks();
} else {
// Show the list of tasks
mTasksView.showTasks(tasks);
// Set the filter label's text.
showFilterLabel();
}
}
}
从上,看出TasksPresenter依赖了TasksRepository、TasksContract.View,即P依赖了M和V;当loadTasks(boolean forceUpdate, final boolean showLoadingUI)被调用后,先从M中获取数据,再调用processTasks(List tasks),其内部调用mTasksView.showTasks(tasks)将数据显示在V上;最后还要说的一点是在TasksPresenter的构造方法中,mTasksView.setPresenter(this) 将P传递给了V
再来看下V如何通过P,来获取数据并显示
TasksFragment,即V的主要代码:
public class TasksFragment extends Fragment implements TasksContract.View {
private TasksContract.Presenter mPresenter;
public TasksFragment() {
// Requires empty public constructor
}
public static TasksFragment newInstance() {
return new TasksFragment();
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mListAdapter = new TasksAdapter(new ArrayList(0), mItemListener);
}
@Override
public void onResume() {
super.onResume();
mPresenter.start();
}
@Override
public void setPresenter(@NonNull TasksContract.Presenter presenter) {
mPresenter = checkNotNull(presenter);
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
mPresenter.loadTasks(false);
}
});
return root;
}
@Override
public void showTasks(List tasks) {
mListAdapter.replaceData(tasks);
mTasksView.setVisibility(View.VISIBLE);
mNoTasksView.setVisibility(View.GONE);
}
}
看TasksFragment的onResume()中,调用了mPresenter.start(),而mPresenter.start()中,就调用了TasksPresenter#loadTasks(false);TasksFragment的onCreateView()中还注册了一个监听回调,即下拉刷新时,也会调用TasksPresenter#loadTasks(false);
P和V的初始化在Activity中完成
TasksActivity的主要代码:
public class TasksActivity extends AppCompatActivity {
private TasksPresenter mTasksPresenter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tasks_act);
TasksFragment tasksFragment =
(TasksFragment) getSupportFragmentManager().findFragmentById(R.id.contentFrame);
if (tasksFragment == null) {
// Create the fragment
tasksFragment = TasksFragment.newInstance();
ActivityUtils.addFragmentToActivity(
getSupportFragmentManager(), tasksFragment, R.id.contentFrame);
}
// Create the presenter
mTasksPresenter = new TasksPresenter(
Injection.provideTasksRepository(getApplicationContext()), tasksFragment);
// Load previously saved state, if available.
if (savedInstanceState != null) {
TasksFilterType currentFiltering =
(TasksFilterType) savedInstanceState.getSerializable(CURRENT_FILTERING_KEY);
mTasksPresenter.setFiltering(currentFiltering);
}
}
}
至此,一条完整的MVP架构实现的业务链就分析完成了