from newbie to
Post on 12-Apr-2017
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Yonatan LevinGoogle Developer Expert
parahalllevin.yonatan
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From Newbie to ...
Disclaimer: It’s my personal opinion
It’s all about “from Junior to Senior”
github.com/parahall/star_wars_movies
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@android:color/background_dark" android:orientation="vertical" tools:context="com.academy.android.starwarsmovies.MainActivity" >
<ImageView android:layout_width="match_parent" android:layout_height="100dp" android:layout_gravity="center_horizontal" android:src="@drawable/logo" />
<ProgressBar android:id="@+id/pb_am_loading" android:layout_width="match_parent" android:layout_height="match_parent" />
<ListView android:id="@+id/lv_am_movie_list" android:layout_width="match_parent" android:layout_height="match_parent" />
</LinearLayout>
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="@android:color/background_dark" android:orientation="horizontal" android:padding="16dp" >
<ImageView android:layout_marginTop="8dp" android:id="@+id/iv_im_movie_poster" android:layout_width="70dp" android:layout_height="98dp" android:scaleType="fitXY" />
<LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginLeft="8dp" android:layout_marginStart="8dp" android:orientation="vertical" > <TextView android:id="@+id/tv_im_movie_name" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="8dp" android:textColor="@android:color/background_light" android:textSize="16sp" android:textStyle="bold" />
<TextView android:id="@+id/tv_im_movie_description" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="8dp" android:textColor="@android:color/background_light" android:textSize="12sp" />
<TextView android:id="@+id/tv_im_movie_date" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="8dp" android:textColor="@android:color/background_light" android:textStyle="italic" />
</LinearLayout>
</LinearLayout>
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.lv_am_movie_list); listView.setVisibility(View.GONE); progressBar = (ProgressBar) findViewById(R.id.pb_am_loading); progressBar.setVisibility(View.VISIBLE); StarWarsAsyncTask asyncTask = new StarWarsAsyncTask(); asyncTask.execute();}
private class StarWarsAsyncTask extends AsyncTask<Void, Void, ArrayList<StarWarsMovie>> {
@Override protected ArrayList<StarWarsMovie> doInBackground(Void... params) { ... }
@Override protected void onPostExecute(ArrayList<StarWarsMovie> starWarsMovies) { … } }
[
{
"name": "Star wars",
"description": "The Imperial Forces, under orders from cruel Darth Vader,
hold Princess Leia hostage in their efforts to...",
"imageUrl": "http://cdn.collider.com/wp-content/uploads/star-wars-movie-
poster.jpg",
"releaseDate": "May 25, 1977"
},
{
"name": "Empire Strikes Back",
"description": "Luke Skywalker, Han Solo, ….",
"imageUrl" :
"https://cdn-images-1.medium.com/max/800/1*q6sBOxkTz7RXOimTLnGrjg.jpeg",
"releaseDate": "May 17, 1980"
},
{ ...
@Override protected ArrayList<StarWarsMovie> doInBackground(Void... params) { String json = ResourcesUtil.loadJson(MainActivity.this); ArrayList<StarWarsMovie> moviesList = null; JSONArray array = new JSONArray(json); moviesList = new ArrayList<>(array.length()); for (int i = 0; i < array.length(); i++) { JSONObject jsonObject = array.getJSONObject(i); String name = jsonObject.getString("name"); String description = jsonObject.getString("description"); String imageUrl = jsonObject.getString("imageUrl"); String releaseDate = jsonObject.getString("releaseDate");
SimpleDateFormat format = new SimpleDateFormat("MMM d, yyyy"); Date date = format.parse(releaseDate); ImageLoader imgLoader = new ImageLoader(getApplicationContext()); Bitmap bitmap = imgLoader.displayImage(imageUrl);
moviesList.add(new StarWarsMovie(name, description, bitmap, date)); } return moviesList; }
public static String loadJson(Context context) { StringBuilder jsonString = new StringBuilder(); URL url = new URL("https://api.starwars.com/movies"); HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); InputStream in = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String line; while ((line = reader.readLine()) != null) { jsonString.append(line); } return jsonString.toString();}
@Override protected void onPostExecute(ArrayList<StarWarsMovie> starWarsMovies) { progressBar.setVisibility(View.GONE); listView.setVisibility(View.VISIBLE); MovieAdapter movieAdapter = new MovieAdapter(MainActivity.this, starWarsMovies); listView.setAdapter(movieAdapter); } }
private class MovieAdapter extends ArrayAdapter<StarWarsMovie> { public MovieAdapter(Context context, ArrayList<StarWarsMovie> users) { super(context, 0, users); }
@Override public View getView(int position, View convertView, ViewGroup parent) { StarWarsMovie starWarsMovie = getItem(position); if (convertView == null) { convertView = LayoutInflater.from(getContext()).inflate(R.layout.item_movie, parent, false); } TextView tvName = (TextView) convertView.findViewById(R.id.tv_im_movie_name); TextView tvDescription = (TextView) convertView.findViewById(R.id.tv_im_movie_description); TextView tvDate = (TextView) convertView.findViewById(R.id.tv_im_movie_date); ImageView ivPoster = (ImageView) convertView.findViewById(R.id.iv_im_movie_poster);
tvName.setText(starWarsMovie.getName()); tvDescription.setText(starWarsMovie.getDescription());
SimpleDateFormat format = new SimpleDateFormat("MMM d, yyyy"); tvDate.setText(format.format(starWarsMovie.getReleaseDate())); ivPoster.setImageBitmap(starWarsMovie.getImageBitmap());
return convertView; } }
Wake Up!VIEWHOLDER!!!!!
Is it only the problem here?
@Override protected ArrayList<StarWarsMovie> doInBackground(Void... params) { String json = ResourcesUtil.loadJson(MainActivity.this); ArrayList<StarWarsMovie> moviesList = null; JSONArray array = new JSONArray(json); moviesList = new ArrayList<>(array.length()); for (int i = 0; i < array.length(); i++) { JSONObject jsonObject = array.getJSONObject(i); String name = jsonObject.getString("name"); String description = jsonObject.getString("description"); String imageUrl = jsonObject.getString("imageUrl"); String releaseDate = jsonObject.getString("releaseDate");
SimpleDateFormat format = new SimpleDateFormat("MMM d, yyyy"); Date date = format.parse(releaseDate); ImageLoader imgLoader = new ImageLoader(getApplicationContext()); Bitmap bitmap = imgLoader.displayImage(imageUrl);
moviesList.add(new StarWarsMovie(name, description, bitmap, date)); } return moviesList; }
Memory Cache File Cache Load from the internet
public class ImageLoader {
MemoryCache memoryCache = new MemoryCache();
FileCache fileCache;
ExecutorService executorService;
public ImageLoader(Context context) {
fileCache = new FileCache(context);
executorService = Executors.newFixedThreadPool(5);
}
public class ImageLoader {
public Bitmap displayImage(String url) {
Bitmap bitmap = memoryCache.get(url);
if (bitmap == null) {
bitmap = getBitmap(url);
memoryCache.put(url, bitmap);
}
return bitmap;
}
private Bitmap getBitmap(String url) { File f = fileCache.getFile(url);
//from SD cache Bitmap b = decodeFile(f); if (b != null) return b;
//from web Bitmap bitmap = null; URL imageUrl = new URL(url); HttpURLConnection conn = (HttpURLConnection) imageUrl.openConnection(); conn.setConnectTimeout(30000); conn.setReadTimeout(30000); conn.setInstanceFollowRedirects(true); InputStream is = conn.getInputStream(); OutputStream os = new FileOutputStream(f); Utils.CopyStream(is, os); os.close(); bitmap = decodeFile(f); return bitmap; }
What if image too large?
//decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f) {
try {
//decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(f), null, o);
//Find the correct scale value. It should be the power of 2.
final int REQUIRED_SIZE = 70;
int width_tmp = o.outWidth, height_tmp = o.outHeight;
int scale = 1;
while (true) {
if (width_tmp / 2 < REQUIRED_SIZE || height_tmp / 2 < REQUIRED_SIZE) break;
width_tmp /= 2;
height_tmp /= 2;
scale *= 2;
}
//decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e) {
}
return null;
}
And it’s just a beginning…
Source: http://konmik.com/post/introduction_to_model_view_presenter_on_android/
Source: http://konmik.com/post/introduction_to_model_view_presenter_on_android/
Complex tasks are split into simpler tasks and are easier to solve.
Smaller objects, less bugs, easier to debug.Testable.
MvpView
MainActivityView
Implements
BasePresenter<T extends MvpView>
Extends
interface abstract
Generic of type
Of Type
Activity
Implements Uses
Creates
ServiceMainPresenter
This was changed
public class StarWarsService extends IntentService {
@Override protected void onHandleIntent(Intent intent) { if (intent != null) { String json = ResourcesUtil.loadJson(this); ArrayList<StarWarsMovie> moviesList = null; JSONArray array = new JSONArray(json); moviesList = new ArrayList<>(array.length()); for (int i = 0; i < array.length(); i++) { JSONObject jsonObject = array.getJSONObject(i); String name = jsonObject.getString("name"); String description = jsonObject.getString("description"); String imageUrl = jsonObject.getString("imageUrl"); String releaseDate = jsonObject.getString("releaseDate"); SimpleDateFormat format = new SimpleDateFormat("MMM d, yyyy"); Date date = format.parse(releaseDate); ImageLoader imgLoader = new ImageLoader(getApplicationContext()); Bitmap bitmap = imgLoader.displayImage(imageUrl); moviesList.add(new StarWarsMovie(name, description, bitmap, date)); }...
public class StarWarsService extends IntentService {
@Override protected void onHandleIntent(Intent intent) { ... Intent response = new Intent(); response.setAction(MainPresenter.LOAD_COMPLETE_ACTION); response.putExtra(MainPresenter.DATA_KEY, moviesList); LocalBroadcastManager.getInstance(this).sendBroadcast(response); } }}
public interface MvpView {
public Context getAppContext();
public Context getActivityContext();
}
public interface MainActivityView extends MvpView {
ListView getListView();
ProgressBar getProgressBar();
}
public abstract class BasePresenter<T extends MvpView> { HandlerThread thread; Looper looper; Handler handler; private T mView;
public void attachView(T t) { thread = new HandlerThread(getClass().getName(),
android.os.Process.THREAD_PRIORITY_BACKGROUND); thread.start(); looper = thread.getLooper(); mView = t; }
public void detachView() { mView = null; if (handler != null) { handler.removeCallbacksAndMessages(null); handler = null; } if (thread != null) thread.quit(); }
}
public abstract class BasePresenter<T extends MvpView> {
public T getView() { return mView; }
public boolean isViewAttached() { return mView != null; }
}
Show me THE PRESENTER!
public class MainPresenter extends BasePresenter<MainActivityView> {
@Override public void attachView(MainActivityView mainActivityView) { super.attachView(mainActivityView); registerLoadDataReceiver();
if (isCacheAvailable()) { updateView(getView().getAppContext(), getView(), movieList); } else { Intent serviceIntent = new Intent(getView().getAppContext(), StarWarsService.class); getView().getAppContext().startService(serviceIntent); } }
public class MainPresenter extends BasePresenter<MainActivityView> {
@Override public void detachView() { unRegisterLoadDataReceiver(); Intent serviceIntent = new Intent(getView().getAppContext(), StarWarsService.class); getView().getAppContext().stopService(serviceIntent); super.detachView(); }
private void updateView(Context context, MainActivityView activityView, ArrayList<StarWarsMovie> list) {
MovieAdapter movieAdapter = new MovieAdapter(context, list); activityView.getListView().setAdapter(movieAdapter);
activityView.getProgressBar().setVisibility(View.GONE); activityView.getListView().setVisibility(View.VISIBLE);}
public class MainPresenter extends BasePresenter<MainActivityView> {
private void registerLoadDataReceiver() { movieDataReceiver = new StarWarsMovieDataReceiver(); LocalBroadcastManager.getInstance(getView().getAppContext()) .registerReceiver(movieDataReceiver, new IntentFilter(LOAD_COMPLETE_ACTION)); }
private void unRegisterLoadDataReceiver() { if (movieDataReceiver != null) { LocalBroadcastManager.getInstance(getView().getAppContext()) .unregisterReceiver(movieDataReceiver); }}
private class StarWarsMovieDataReceiver extends BroadcastReceiver {
@Override public void onReceive(Context context, Intent intent) { if (intent.getAction().equals(LOAD_COMPLETE_ACTION)) {
if (isViewAttached()) { MainActivityView activityView = getView(); movieList = (ArrayList<StarWarsMovie>) intent.getSerializableExtra(DATA_KEY); updateView(context, activityView, movieList); } } }}
Activity?
public class MainActivity extends AppCompatActivity implements MainActivityView {
... public static MainPresenter mainPresenter;
@Override protected void onCreate(Bundle savedInstanceState) { ... ... if (mainPresenter == null) { mainPresenter = new MainPresenter(); } mainPresenter.attachView(this); }
@Override protected void onDestroy() { super.onDestroy(); mainPresenter.detachView(); if (isFinishing()) mainPresenter = null; }
@Override public Context getAppContext() { return getApplicationContext(); }
@Override public Context getActivityContext() { return this; }
@Override public ListView getListView() { return listView; }
@Override public ProgressBar getProgressBar() { return progressBar; }}
ATTENTION!
public class MainActivity extends AppCompatActivity implements MainActivityView {
@Override public Context getAppContext() { return getApplicationContext(); }
@Override public Context getActivityContext() { return this; }
@Override public ListView getListView() { return listView; }
@Override public ProgressBar getProgressBar() { return progressBar; }}
Questions ?
There are other ways to retain presenter
- Let him go (Not so user friendly)
- Static (Could be issue with multiple
instance)
- Fragments - setRetainInstance(true) (what
about nested fragments)?
- Loaders (Tricky when onLoaderFinished()
called within lifecycle)
- Static map. Nucleus.
Questions ?
We can do more. It’s just a beginning
compile 'com.squareup.retrofit2:retrofit:2.1.0'
compile 'com.squareup.retrofit2:converter-gson:2.1.0'
public interface StarwarsApi {
@GET("/movies/{movie_id}")
Call<StarWarsMovie> getMovie(@Path("movie_id") int id);
@GET("/movies")
Call<ArrayList<StarWarsMovie>> listMovies();
}
public static ArrayList<StarWarsMovie> getStarWarsMovies() {
ArrayList<StarWarsMovie> moviesList = null; Retrofit retrofit = new Retrofit.Builder().baseUrl("https://api.starwars.com/") .addConverterFactory( GsonConverterFactory.create(new GsonBuilder().setDateFormat("MMM d, yyyy").create())) .build();
StarwarsApi starwarsApi = retrofit.create(StarwarsApi.class);
Call<ArrayList<StarWarsMovie>> arrayListCall = starwarsApi.listMovies(); Response<ArrayList<StarWarsMovie>> listResponse = arrayListCall.execute(); moviesList = listResponse.body(); return moviesList;}
Memory Cache File Cache Load from the internet
ImageLoader imgLoader = new ImageLoader(getApplicationContext());
Bitmap bitmap = imgLoader.displayImage(imageUrl);
compile 'com.github.bumptech.glide:glide:3.7.0'
bitmap =
Glide.with(getApplicationContext()).load(imageUrl).asBitmap().into(100,
100).get();
More read
https://futurestud.io/tutorials/glide-getting-started
https://inthecheesefactory.com/blog/get-to-know-glide-recommended-by-google/en
findViewById no more
compile 'com.jakewharton:butterknife:8.4.0'
annotationProcessor 'com.jakewharton:butterknife-compiler:8.4.0'
public class MainActivity extends AppCompatActivity implements MainActivityView {
private @BindView(R.id.lv_am_movie_list) ListView listView; private @BindView(R.id.pb_am_loading) ProgressBar progressBar;
@Override protected void onCreate(Bundle savedInstanceState) { …
listView = (ListView) findViewById(R.id.lv_am_movie_list);
progressBar = (ProgressBar) findViewById(R.id.pb_am_loading);
ButterKnife.bind(this); listView.setVisibility(View.GONE); progressBar.setVisibility(View.VISIBLE);
}
static class ViewHolder {
@BindView(R.id.tv_im_movie_name) TextView tvName;
@BindView(R.id.tv_im_movie_description) TextView tvDescription;
@BindView(R.id.tv_im_movie_date) TextView tvDate;
@BindView(R.id.iv_im_movie_poster) ImageView ivPoster;
public ViewHolder(View view) {
ButterKnife.bind(this, view);
}
}
private class MovieAdapter extends ArrayAdapter<StarWarsMovie> {
public View getView(int position, View convertView, ViewGroup parent)
{
if (convertView == null) {
convertView =
LayoutInflater.from(getContext()).inflate(R.layout.item_movie, parent,
false);
holder = new ViewHolder();
holder.tvName = (TextView)
convertView.findViewById(R.id.tv_im_movie_name);
holder.tvDescription = (TextView)
convertView.findViewById(R.id.tv_im_movie_description);
holder.tvDate = (TextView)
convertView.findViewById(R.id.tv_im_movie_date);
holder.ivPoster = (ImageView)
convertView.findViewById(R.id.iv_im_movie_poster);
convertView.setTag(holder);
...
Can we do better?
Json Parsing
public class StarWarsMovie {
private String name;
private String description;
private BitmapString imageBitmapUrl;
private Date releaseDate;
}
compile 'com.google.code.gson:gson:2.8.0'
@Override protected void onHandleIntent(Intent intent) {
if (intent != null) {
...
Gson gson = new GsonBuilder().setDateFormat("MMM d,
yyyy").create();
ArrayList<StarWarsMovie> moviesList =
gson.fromJson(json, new TypeToken<ArrayList<StarWarsMovie>>() {
}.getType());
…
}
}
private class MovieAdapter extends ArrayAdapter<StarWarsMovie> {
@NonNull @Override public View getView(int position, View
convertView, ViewGroup parent) {
...
Glide.with(getContext())
.load(starWarsMovie.getImageUrl())
.placeholder(R.drawable.placeholder)
.into(holder.ivPoster);
return convertView;
}
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