java - 这段代码中的 init() 方法有什么用？

Question

我正在尝试学习如何使用 JSON，并且我将从教程中查看此代码，并且有一个 init() 方法。根据我在网上发现的信息，init()通常用作小程序的入口点。如果是这样，那么为什么 init() 出现在 Android 应用程序代码中而不是网站代码中？有人可以解释一下它的原因吗？这是在 android 中使用 JSON 时常见的情况还是不常见的情况？

public class MainActivity extends AppCompatActivity {

private RecyclerView mRestaurantRecyclerView;
private RestaurantAdapter mAdapter;
private ArrayList<Restaurant> mRestaurantCollection;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    init();
    new FetchDataTask().execute();
}

private void init() {
    mRestaurantRecyclerView = (RecyclerView) findViewById(R.id.restaurant_recycler);
    mRestaurantRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    mRestaurantRecyclerView.setHasFixedSize(true);
    mRestaurantCollection = new ArrayList<>();
    mAdapter = new RestaurantAdapter(mRestaurantCollection, this);
    mRestaurantRecyclerView.setAdapter(mAdapter);
}

public class FetchDataTask extends AsyncTask<Void, Void, Void> {
    private String mZomatoString;

    @Override
    protected Void doInBackground(Void... params) {
        HttpURLConnection urlConnection = null;
        BufferedReader reader = null;
        Uri builtUri = Uri.parse(getString(R.string.zomato_api));
        URL url;
        try {
            url = new URL(builtUri.toString());
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setRequestMethod("GET");
            urlConnection.setRequestProperty("user-key", "acfd3e623c5f01289bd87aaaff1926c1");
            urlConnection.connect();

            InputStream inputStream = urlConnection.getInputStream();
            StringBuffer buffer = new StringBuffer();
            if (inputStream == null) {
                //Nothing to do
                return null;
            }

            reader = new BufferedReader(new InputStreamReader(inputStream));

            String line;
            while ((line = reader.readLine()) != null) {
                buffer.append(line + "\n");
            }

            if (buffer.length() == 0) {
                return null;
            }

            mZomatoString = buffer.toString();
            JSONObject jsonObject = new JSONObject(mZomatoString);

            Log.v("Response", jsonObject.toString());

            JSONArray restaurantsArray = jsonObject.getJSONArray("restaurants");

            //list = new ArrayList<>();
            for (int i = 0; i < restaurantsArray.length(); i++) {

                Log.v("BRAD_", i + "");
                String name;
                String address;
                String currency;
                String imageUrl;
                long lon;
                long lat;
                long cost;
                float rating;


                JSONObject jRestaurant = (JSONObject) restaurantsArray.get(i);
                jRestaurant = jRestaurant.getJSONObject("restaurant");
                JSONObject jLocattion = jRestaurant.getJSONObject("location");
                JSONObject jRating = jRestaurant.getJSONObject("user_rating");


                name = jRestaurant.getString("name");
                address = jLocattion.getString("address");
                lat = jLocattion.getLong("latitude");
                lon = jLocattion.getLong("longitude");
                currency = jRestaurant.getString("currency");
                cost = jRestaurant.getInt("average_cost_for_two");
                imageUrl = jRestaurant.getString("thumb");
                rating = (float) jRating.getDouble("aggregate_rating");


                Restaurant restaurant = new Restaurant();
                restaurant.setName(name);
                restaurant.setAddress(address);
                restaurant.setLatitiude(lat);
                restaurant.setLongitude(lon);
                restaurant.setCurrency(currency);
                restaurant.setCost(String.valueOf(cost));
                restaurant.setImageUrl(imageUrl);
                restaurant.setRating(String.valueOf(rating));

                mRestaurantCollection.add(restaurant);
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (JSONException e) {
            e.printStackTrace();
        } finally {
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
            if (reader != null) {
                try {
                    reader.close();
                } catch (final IOException e) {
                    Log.e("MainActivity", "Error closing stream", e);
                }
            }
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        mAdapter.notifyDataSetChanged();
    }
}

Answer 1

基本上是 init 方法设置 recyclerview 及其配置

mRestaurantRecyclerView = (RecyclerView) findViewById(R.id.restaurant_recycler);

从xml定义回收器并将其放入变量mRestaurantRecyclerVIew

mRestaurantRecyclerView.setLayoutManager(new LinearLayoutManager(this));

设置recyclerview的显示方式，稍后应在项目中定义

mRestaurantRecyclerView.setHasFixedSize(true);

正如函数所说，rv将具有固定大小，您也可以引用此链接了解此特定函数Understanding RecyclerView setHasFixedSize

 mRestaurantCollection = new ArrayList<>(); 

这个 mRestaurantCollection 将保存将在 recyclerview 中显示的数据列表。

mAdapter = new RestaurantAdapter(mRestaurantCollection, this);
mRestaurantRecyclerView.setAdapter(mAdapter);

最后但不是列表，这两行代码将通过适配器将数据与recyclerview Hook 。第一行是启动适配器插入 2 个参数，即数据和上下文，第二行告诉 recyclerview，“嘿，我是你的适配器，显示这个。”。

PS:最后但不是列表意味着一个笑话。哈哈，如果不好笑的话请原谅。