In 2008 Android app code had a lot of boilerplate, and was very error prone.
More code.. more bugs!
Now it doesn't have to be... but that is an option that each developer needs to take!
30. public class TasksFragment extends Fragment implements TasksContract.View {
private TasksContract.Presenter mPresenter;
private TasksAdapter mListAdapter;
private View mNoTasksView;
private ImageView mNoTaskIcon;
private TextView mNoTaskMainView;
private TextView mNoTaskAddView;
private LinearLayout mTasksView;
private TextView mFilteringLabelView;
...
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mListAdapter = new TasksAdapter(new ArrayList<Task>(0), mItemListener);
}
@Override
public void onResume() {
super.onResume();
mPresenter.start();
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.tasks_frag, container, false);
// Set up tasks view
ListView listView = (ListView) root.findViewById(R.id.tasks_list);
listView.setAdapter(mListAdapter);
mFilteringLabelView = (TextView) root.findViewById(R.id.filteringLabel);
mTasksView = (LinearLayout) root.findViewById(R.id.tasksLL);
// Set up no tasks view
mNoTasksView = root.findViewById(R.id.noTasks);
mNoTaskIcon = (ImageView) root.findViewById(R.id.noTasksIcon);
mNoTaskMainView = (TextView) root.findViewById(R.id.noTasksMain);
mNoTaskAddView = (TextView) root.findViewById(R.id.noTasksAdd);
mNoTaskAddView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
showAddTask();
}
});
...
setHasOptionsMenu(true);
return root;
}
...
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 result(int requestCode, int resultCode) {
// If a task was successfully added, show snackbar
if (AddEditTaskActivity.REQUEST_ADD_TASK == requestCode
&& Activity.RESULT_OK == resultCode) {
mTasksView.showSuccessfullySavedMessage();
}
}
@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();
}
mTasksRepository.getTasks(new TasksDataSource.LoadTasksCallback() {
@Override
public void onTasksLoaded(List<Task> tasks) {
List<Task> tasksToShow = new ArrayList<Task>()
// We filter the tasks based on the requestType
for (Task task : tasks) {
switch (mCurrentFiltering) {
case ALL_TASKS:
tasksToShow.add(task);
break;
case ACTIVE_TASKS:
public class TasksRepository implements TasksDataSource {
private static TasksRepository INSTANCE = null;
private final TasksDataSource mTasksRemoteDataSource;
private final TasksDataSource mTasksLocalDataSource;
/**
* This variable has package local visibility so it can be accessed from tests.
*/
Map<String, Task> mCachedTasks;
/**
* Returns the single instance of this class, creating it if necessary.
*
* @param tasksRemoteDataSource the backend data source
* @param tasksLocalDataSource the device storage data source
* @return the {@link TasksRepository} instance
*/
public static TasksRepository getInstance(TasksDataSource tasksRemoteDataSource,
TasksDataSource tasksLocalDataSource) {
if (INSTANCE == null) {
INSTANCE = new TasksRepository(tasksRemoteDataSource, tasksLocalDataSource);
}
return INSTANCE;
}
/**
* Gets tasks from cache, local data source (SQLite) or remote data source, whichever is
* available first.
*/
@Override
public void getTasks(@NonNull final LoadTasksCallback callback) {
checkNotNull(callback);
// Respond immediately with cache if available and not dirty
if (mCachedTasks != null && !mCacheIsDirty) {
callback.onTasksLoaded(new ArrayList<>(mCachedTasks.values()));
return;
}
if (mCacheIsDirty) {
// If the cache is dirty we need to fetch new data from the network.
getTasksFromRemoteDataSource(callback);
} else {
// Query the local storage if available. If not, query the network.
mTasksLocalDataSource.getTasks(new LoadTasksCallback() {
@Override
public void onTasksLoaded(List<Task> tasks) {
refreshCache(tasks);
callback.onTasksLoaded(new ArrayList<>(mCachedTasks.values()));
}
@Override
public void onDataNotAvailable() {
getTasksFromRemoteDataSource(callback);
}
31. public class TasksFragment extends Fragment implements TasksContract.View {
private TasksContract.Presenter mPresenter;
private TasksAdapter mListAdapter;
private View mNoTasksView;
private ImageView mNoTaskIcon;
private TextView mNoTaskMainView;
private TextView mNoTaskAddView;
private LinearLayout mTasksView;
private TextView mFilteringLabelView;
...
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mListAdapter = new TasksAdapter(new ArrayList<Task>(0), mItemListener);
}
@Override
public void onResume() {
super.onResume();
mPresenter.start();
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.tasks_frag, container, false);
// Set up tasks view
ListView listView = (ListView) root.findViewById(R.id.tasks_list);
listView.setAdapter(mListAdapter);
mFilteringLabelView = (TextView) root.findViewById(R.id.filteringLabel);
mTasksView = (LinearLayout) root.findViewById(R.id.tasksLL);
// Set up no tasks view
mNoTasksView = root.findViewById(R.id.noTasks);
mNoTaskIcon = (ImageView) root.findViewById(R.id.noTasksIcon);
mNoTaskMainView = (TextView) root.findViewById(R.id.noTasksMain);
mNoTaskAddView = (TextView) root.findViewById(R.id.noTasksAdd);
mNoTaskAddView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
showAddTask();
}
});
...
setHasOptionsMenu(true);
return root;
}
...
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 result(int requestCode, int resultCode) {
// If a task was successfully added, show snackbar
if (AddEditTaskActivity.REQUEST_ADD_TASK == requestCode
&& Activity.RESULT_OK == resultCode) {
mTasksView.showSuccessfullySavedMessage();
}
}
@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();
}
mTasksRepository.getTasks(new TasksDataSource.LoadTasksCallback() {
@Override
public void onTasksLoaded(List<Task> tasks) {
List<Task> tasksToShow = new ArrayList<Task>()
// We filter the tasks based on the requestType
for (Task task : tasks) {
switch (mCurrentFiltering) {
case ALL_TASKS:
tasksToShow.add(task);
break;
case ACTIVE_TASKS:
public class TasksRepository implements TasksDataSource {
private static TasksRepository INSTANCE = null;
private final TasksDataSource mTasksRemoteDataSource;
private final TasksDataSource mTasksLocalDataSource;
/**
* This variable has package local visibility so it can be accessed from tests.
*/
Map<String, Task> mCachedTasks;
/**
* Returns the single instance of this class, creating it if necessary.
*
* @param tasksRemoteDataSource the backend data source
* @param tasksLocalDataSource the device storage data source
* @return the {@link TasksRepository} instance
*/
public static TasksRepository getInstance(TasksDataSource tasksRemoteDataSource,
TasksDataSource tasksLocalDataSource) {
if (INSTANCE == null) {
INSTANCE = new TasksRepository(tasksRemoteDataSource, tasksLocalDataSource);
}
return INSTANCE;
}
/**
* Gets tasks from cache, local data source (SQLite) or remote data source, whichever is
* available first.
*/
@Override
public void getTasks(@NonNull final LoadTasksCallback callback) {
checkNotNull(callback);
// Respond immediately with cache if available and not dirty
if (mCachedTasks != null && !mCacheIsDirty) {
callback.onTasksLoaded(new ArrayList<>(mCachedTasks.values()));
return;
}
if (mCacheIsDirty) {
// If the cache is dirty we need to fetch new data from the network.
getTasksFromRemoteDataSource(callback);
} else {
// Query the local storage if available. If not, query the network.
mTasksLocalDataSource.getTasks(new LoadTasksCallback() {
@Override
public void onTasksLoaded(List<Task> tasks) {
refreshCache(tasks);
callback.onTasksLoaded(new ArrayList<>(mCachedTasks.values()));
}
@Override
public void onDataNotAvailable() {
getTasksFromRemoteDataSource(callback);
}
32. public class TasksFragment extends Fragment implements TasksContract.View {
private TasksContract.Presenter mPresenter;
private TasksAdapter mListAdapter;
private View mNoTasksView;
private ImageView mNoTaskIcon;
private TextView mNoTaskMainView;
private TextView mNoTaskAddView;
private LinearLayout mTasksView;
private TextView mFilteringLabelView;
...
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mListAdapter = new TasksAdapter(new ArrayList<Task>(0), mItemListener);
}
@Override
public void onResume() {
super.onResume();
mPresenter.start();
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.tasks_frag, container, false);
// Set up tasks view
ListView listView = (ListView) root.findViewById(R.id.tasks_list);
listView.setAdapter(mListAdapter);
mFilteringLabelView = (TextView) root.findViewById(R.id.filteringLabel);
mTasksView = (LinearLayout) root.findViewById(R.id.tasksLL);
// Set up no tasks view
mNoTasksView = root.findViewById(R.id.noTasks);
mNoTaskIcon = (ImageView) root.findViewById(R.id.noTasksIcon);
mNoTaskMainView = (TextView) root.findViewById(R.id.noTasksMain);
mNoTaskAddView = (TextView) root.findViewById(R.id.noTasksAdd);
mNoTaskAddView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
showAddTask();
}
});
...
setHasOptionsMenu(true);
return root;
}
...
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
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 result(int requestCode, int resultCode) {
// If a task was successfully added, show snackbar
if (AddEditTaskActivity.REQUEST_ADD_TASK == requestCode && Activity.RESULT_OK == re
mTasksView.showSuccessfullySavedMessage();
}
}
@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 know
// 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<Task> tasks) {
List<Task> tasksToShow = new ArrayList<Task>()
// We filter the tasks based on the requestType
for (Task task : tasks) {
switch (mCurrentFiltering) {
case ALL_TASKS:
tasksToShow.add(task);
break;
public class TasksRepository implements TasksDataSource {
private static TasksRepository INSTANCE = null;
private final TasksDataSource mTasksRemoteDataSource;
private final TasksDataSource mTasksLocalDataSource;
/**
* This variable has package local visibility so it can be accessed from tests.
*/
Map<String, Task> mCachedTasks;
/**
* Returns the single instance of this class, creating it if necessary.
*
* @param tasksRemoteDataSource the backend data source
* @param tasksLocalDataSource the device storage data source
* @return the {@link TasksRepository} instance
*/
public static TasksRepository getInstance(TasksDataSource tasksRemoteDataSource,
TasksDataSource tasksLocalDataSource) {
if (INSTANCE == null) {
INSTANCE = new TasksRepository(tasksRemoteDataSource, tasksLocalDataSource);
}
return INSTANCE;
}
/**
* Gets tasks from cache, local data source (SQLite) or remote data source, whichever is
* available first.
*/
@Override
public void getTasks(@NonNull final LoadTasksCallback callback) {
checkNotNull(callback);
// Respond immediately with cache if available and not dirty
if (mCachedTasks != null && !mCacheIsDirty) {
callback.onTasksLoaded(new ArrayList<>(mCachedTasks.values()));
return;
}
if (mCacheIsDirty) {
// If the cache is dirty we need to fetch new data from the network.
getTasksFromRemoteDataSource(callback);
} else {
// Query the local storage if available. If not, query the network.
mTasksLocalDataSource.getTasks(new LoadTasksCallback() {
@Override
public void onTasksLoaded(List<Task> tasks) {
refreshCache(tasks);
callback.onTasksLoaded(new ArrayList<>(mCachedTasks.values()));
}
@Override
public void onDataNotAvailable() {
getTasksFromRemoteDataSource(callback);
}
33. Consists of Model, View, and Presenter layers;
View delegates user input to Presenter;
All layers should have a 1 to 1 relation;
View and Model aren’t tightly coupled (separation of concerns);
Easy unit testing (interface for Presenter layer is easily mocked);
MVP
90. class MainViewModel(private val service: WeatherService)
: ViewModel() {
val weatherTextValue = MutableLiveData<String>()
val inProgress = MutableLiveData<Boolean>()
private var disposable: Disposable? = null
fun onRefreshWeatherClicked() {
inProgress.value = true
disposable = service.requestWeather()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(this::onWeatherResponse)
}
override fun onCleared() {
disposable?.dispose()
}
private fun onWeatherResponse(response: String) {
inProgress.value = false
weatherTextValue.value = response
}
}
What if I don’t
have network and
want to wait for it
to update screen?
Because..
!
class MainActivity : AppCompatActivity() {
@Inject lateinit var viewModelFactory: MainViewModelFactory
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
Dependencies.inject(this)
val binding = MainActivityBinding
.inflate(LayoutInflater.from(this)
binding.setLifecycleOwner(this)
setContentView(binding.root)
binding.button.clicks()
.subscribe { viewModel.onRefreshWeatherClicked() }
}
private val viewModel : MainViewModel by lazy{
ViewModelProviders.of(this, viewModelFactory)
.get(MainViewModel::class.java)
}
93. class MainActivity : AppCompatActivity() {
@Inject lateinit var viewModelFactory: MainViewModelFactory
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
Dependencies.inject(this)
val binding = MainActivityBinding
.inflate(LayoutInflater.from(this)
binding.setLifecycleOwner(this)
setContentView(binding.root)
binding.button.clicks()
.subscribe { viewModel.onRefreshWeatherClicked() }
}
private val viewModel : MainViewModel by lazy{
ViewModelProviders.of(this, viewModelFactory)
.get(MainViewModel::class.java)
}
val constraints: Constraints = Constraints.Builder()
.setRequiredNetworkType(NetworkType.CONNECTED)
.build()
val work: OneTimeWorkRequest = OneTimeWorkRequest
.Builder(PortugalChampionWorker::class.java)
.setConstraints(constraints).build()
WorkManager.getInstance().enqueue(work)
workId = work.id
WorkManager.getInstance().getStatusById(workId)
.observe(this, Observer { status ->
if (status?.state?.isFinished == true) {
val myResult = status.outputData.getString(KEY_RESULT,
myDefaultValue)
textValue.value = myResult
}
})
}
override fun onCleared() {
//Want to cancel when exiting screen?
workId?.let{
WorkManager.getInstance().cancelWorkById(it)
}
}
}
class PortugalChampionWorker : Worker() {
override fun doWork(): Result {
//No need for querying.. the result is clear.. success!
return Result.SUCCESS
}
}
Magic!
class MainViewModel(private val service: FootballService) : ViewModel() {
val textValue = MutableLiveData<String>()
val inProgress = MutableLiveData<Int>()
val workId : UUID? = null
private var disposable: Disposable? = null
fun onButtonClicked() {
inProgress.value = View.VISIBLE
94. val constraints: Constraints = Constraints.Builder()
.setRequiredNetworkType(NetworkType.CONNECTED)
.build()
val work: OneTimeWorkRequest = OneTimeWorkRequest
.Builder(PortugalChampionWorker::class.java)
.setConstraints(constraints).build()
WorkManager.getInstance().enqueue(work)
workId = work.id
WorkManager.getInstance().getStatusById(workId)
.observe(this, Observer { status ->
if (status != null && status.state.isFinished) {
val myResult = status.outputData.getString(KEY_RESULT,
myDefaultValue)
textValue.value = myResult
}
})
}
override fun onCleared() {
//Want to cancel when exiting screen?
workId?.let{
WorkManager.getInstance().cancelWorkById(it)
}
}
}
class PortugalChampionWorker : Worker() {
override fun doWork(): Result {
//No need for querying.. the result is clear.. success!
return Result.SUCCESS
}
}
class MainActivity : AppCompatActivity() {
@Inject lateinit var viewModelFactory: MainViewModelFactory
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
Dependencies.inject(this)
val binding = MainActivityBinding
.inflate(LayoutInflater.from(this)
binding.setLifecycleOwner(this)
setContentView(binding.root)
binding.button.clicks()
.subscribe { viewModel.onRefreshWeatherClicked() }
}
private val viewModel : MainViewModel by lazy{
ViewModelProviders.of(this, viewModelFactory)
.get(MainViewModel::class.java)
}
Hum… must finish?
You are kind of
bullshitting here,
aren’t you Pedro?
class MainViewModel(private val service: FootballService) : ViewModel() {
val textValue = MutableLiveData<String>()
val inProgress = MutableLiveData<Int>()
val workId : UUID? = null
private var disposable: Disposable? = null
fun onButtonClicked() {
inProgress.value = View.VISIBLE
But I forgive you!