接口回調(diào)

在對(duì)象中，有些事件不確定什么時(shí)候能完成寨躁，此時(shí)可以通過(guò)預(yù)留監(jiān)督機(jī)制，關(guān)注事件的變化，這個(gè)機(jī)制即回調(diào)。

舉個(gè)例子
模擬下載器腋，實(shí)施監(jiān)督下載的進(jìn)度翎冲，當(dāng)100%時(shí)赏壹，提醒下載完成

1.  建立一個(gè)下載進(jìn)度的類
    需要監(jiān)督加載的進(jìn)度，因此方法內(nèi)需要一個(gè)監(jiān)督進(jìn)度的形參接口
class Progress {

    public void loadProgress(IProgressListener progressListener) {
        //模擬進(jìn)度
        for (int i = 1; i <= 100; i++) {
            //進(jìn)度每改變一次，即調(diào)用更新一次監(jiān)督的數(shù)據(jù)
            progressListener.curProgress(i);
        }
    }
}


2.  建立監(jiān)聽(tīng)的回調(diào)接口数苫，用來(lái)監(jiān)聽(tīng)進(jìn)度
interface IProgressListener {
    void curProgress(int curProgress);
}


3.運(yùn)行調(diào)用
  實(shí)際還是對(duì)多態(tài)的運(yùn)用
  當(dāng)Progress類調(diào)用loadProgress(IProgressListener progressListener)時(shí)
  傳入的實(shí)參是一個(gè)匿名內(nèi)部類谈山，也是IProgressListener的子類
  相當(dāng)于 IProgressListener progressListener = new 子類();
  此時(shí)調(diào)用的是子類的實(shí)現(xiàn)斜脂。

public class Main {

    public static void main(String[] args) {
        Progress progress = new Progress();

        progress.loadProgress(new IProgressListener() {
            @Override
            public void curProgress(int curProgress) {
                System.out.printf("curProgress：" + curProgress + "\r\n");
                if (curProgress == 100)
                    System.out.printf("下載完成");
            }
        });
    }
}

OkHttp

Android網(wǎng)絡(luò)請(qǐng)求的變遷

OkHttp的基本用法

前置工作
1.  添加依賴
OkHttp依賴：implementation 'com.squareup.okhttp3:okhttp:3.11.0'
Gson依賴：implementation 'com.google.code.gson:gson:2.8.5'

2.  Android在做網(wǎng)絡(luò)請(qǐng)求時(shí)要添加權(quán)限
<uses-permission android:name="android.permission.INTERNET" />

注意
Android P 限制了明文流量的網(wǎng)絡(luò)請(qǐng)求涝动，非加密的流量請(qǐng)求都會(huì)被系統(tǒng)禁止鼻吮。
如果 WebView 的 url 用 http 協(xié)議，同樣會(huì)出現(xiàn)加載失敗肥照，https 不受影響。

如果當(dāng)前應(yīng)用的請(qǐng)求是 htttp 而非 https梧税，系統(tǒng)會(huì)禁止當(dāng)前應(yīng)用進(jìn)行該請(qǐng)求缓醋。
在 Android P 版本如果使用了明文流量褪贵，OkHttp3會(huì)拋出
CLEARTEXT communication to " + host + " not permitted by network security policy異常

解決方案
服務(wù)器和客戶端的請(qǐng)求最好都用https

OkHttp提供的API

Get請(qǐng)求
1.  首先創(chuàng)建OkHttpClient
OkHttpClient okHttpClient = new OkHttpClient();


2.  發(fā)送請(qǐng)求需要構(gòu)建Request對(duì)象
Request request = new Request.Builder()
                .url(requestUrl())
                .build();


3.  okHttpClient 調(diào)用newCall()創(chuàng)建一個(gè)Call對(duì)象橄镜，并調(diào)用enqueue()
發(fā)送請(qǐng)求并獲取服務(wù)器返回的數(shù)據(jù)姊氓。
okHttpClient.newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(Call call, IOException e) {

        }

        @Override
        public void onResponse(Call call, Response response) throws IOException {

            if (response.isSuccessful()) {
                String resJson = response.body().string();
                Gson gson = new Gson();
                User user = gson.fromJson(resJson, User.class);
            }
        }
});


Post請(qǐng)求
1. 需要構(gòu)建一個(gè)RequestBody對(duì)象來(lái)存放提交的參數(shù)
RequestBody body = new FormBody.Builder()
                .add("userName", getUserName())
                .add("userCode", getUserCode())
                .build();


2.  將body 添加到Request.Builder中
Request request = new Request.Builder()
                .url(requestUrl())
                .post(body)
                .build();

舉個(gè)例子
客戶端向服務(wù)器發(fā)送用戶輸入的用戶名瘦锹，用戶編號(hào)
服務(wù)端返回用戶的信息


1.  服務(wù)端
Module類
public class User {
    String name;
    int code;
    String info;
}


@WebServlet(value = "/user")
public class UserServlet extends HttpServlet {

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {

        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=UTF-8");

        Gson gson = new Gson();
        String userName = req.getParameter("userName");
        String userCode = req.getParameter("userCode");

        if (userName.equals("admin") && userCode.equals("123")) {
            User user = new User("admin", 1, "演示信息");
            resp.getWriter().println(gson.toJson(user));
        }
    }
}

2.  客戶端

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";

    private EditText mEtUserName;
    private EditText mEtUserCode;
    private Button mBtnQuery;
    private TextView mTvShowUserInfo;

    @SuppressLint("HandlerLeak")
    private Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case 1:
                    User user = (User) msg.obj;
                    showUserInfo(user);
                    break;
            }
        }
    };

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

        initView();
        initEvent();
    }

    private void initEvent() {
        mBtnQuery.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                getUserInfo();
            }
        });
    }

    //網(wǎng)絡(luò)請(qǐng)求
    private void getUserInfo() {
        OkHttpClient okHttpClient = new OkHttpClient();
        RequestBody body = new FormBody.Builder()
                .add("userName", getUserName())
                .add("userCode", getUserCode())
                .build();

        final Request request = new Request.Builder()
                .url(requestUrl())
                .post(body)
                .build();

        okHttpClient.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {

            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {

                if (response.isSuccessful()) {
                    String resJson = response.body().string();
                    Gson gson = new Gson();
                    User user = gson.fromJson(resJson, User.class);
                    Message message = Message.obtain();
                    message.what = 1;
                    message.obj = user;
                    mHandler.sendMessage(message);
                }
            }
        });
    }

    private void initView() {
        mEtUserName = findViewById(R.id.et_user_name);
        mEtUserCode = findViewById(R.id.et_user_code);
        mBtnQuery = findViewById(R.id.btn_query_data);
        mTvShowUserInfo = findViewById(R.id.tv_user_info_show);
    }

    private String getUserName() {
        return mEtUserName.getText().toString();
    }

    private String getUserCode() {
        return mEtUserCode.getText().toString();
    }

    private void showUserInfo(User user) {
        StringBuilder builder = new StringBuilder();
        builder.append("UserName：" + user.getName())
                .append("\r\n")
                .append("UserCode：" + user.getCode())
                .append("\r\n")
                .append("UserInfo：" + user.getInfo());
        mTvShowUserInfo.setText(builder.toString());
    }

    private String requestUrl() {
        return "http://192.168.1.104:8080/user";
    }
}

OkHttp封裝

思路
通過(guò)觀察OkHttp贴妻，不難發(fā)現(xiàn)所有的請(qǐng)求都是通過(guò)Request這個(gè)類構(gòu)建
為了保證不浪費(fèi)資源，將OkHttp設(shè)置為單例模式蝙斜。

1.  用枚舉區(qū)分Get名惩，Post，設(shè)置對(duì)外調(diào)用方法孕荠，獲取網(wǎng)絡(luò)請(qǐng)求
    傳遞參數(shù)
      1.請(qǐng)求的路徑
      2.post請(qǐng)求時(shí)傳遞的參數(shù)
      3.一個(gè)用于監(jiān)測(cè)請(qǐng)求完成的回調(diào)類

2.  定義OkHttp的請(qǐng)求doRequest()方法娩鹉，用于監(jiān)聽(tīng)請(qǐng)求成功失敗攻谁，請(qǐng)求前的狀態(tài)
    傳遞參數(shù)
      1.構(gòu)建的Request類
      2.監(jiān)聽(tīng)回調(diào)類

3.  所有請(qǐng)求都用異步在子線程操作，修改UI需要Handler發(fā)送到主線程
這就需要根據(jù)成功失敗的回調(diào)弯予，創(chuàng)建發(fā)送的Handler方法

4.  定義回調(diào)類
    1.請(qǐng)求成功
    2.請(qǐng)求失敗

5.  設(shè)置回調(diào)的包裝類戚宦，幫助簡(jiǎn)化構(gòu)建不必要的方法

1.  設(shè)置回調(diào)類

public abstract class IBaseCallBack<T> {

    public Type mType;

    public IBaseCallBack() {
        mType = getSuperclassTypeParameter(getClass());
    }

    /**
     * 將Type類型轉(zhuǎn)換成Gson，解析
     */
    static Type getSuperclassTypeParameter(Class<?> subclass) {
        Type superclass = subclass.getGenericSuperclass();
        if (superclass instanceof Class) {
            throw new RuntimeException("Missing type parameter.");
        }
        ParameterizedType parameterized = (ParameterizedType) superclass;
        return $Gson$Types.canonicalize(parameterized.getActualTypeArguments()[0]);
    }

    //請(qǐng)求成功前回調(diào)
    public abstract void onRequestBefore();

    //網(wǎng)絡(luò)請(qǐng)求成功后根據(jù)返回碼調(diào)用
    public abstract void onSuccess(Response response, T t);

    //請(qǐng)求失敗時(shí)
    public abstract void onFailure(Call call, Exception e);
}

2.  將OkHttp封裝

public class OkHttpHelper {

    private static OkHttpHelper mOkHttpHelper;
    private static OkHttpClient mOkHttpClient;

    private static Gson mGson;
    private Handler mHandler;

    private OkHttpHelper() {
        mOkHttpClient = new OkHttpClient();
        mGson = new Gson();

        //每發(fā)現(xiàn)一條消息就推送到Handler
        mHandler = new Handler(Looper.getMainLooper());
    }

    public static OkHttpHelper getOkHttpHelperInstance() {
        if (mOkHttpHelper == null) {
            synchronized (OkHttpHelper.class) {
                if (mOkHttpHelper == null) {
                    mOkHttpHelper = new OkHttpHelper();
                }
            }
        }
        return mOkHttpHelper;
    }

    //來(lái)區(qū)別請(qǐng)求的類型
    enum HttpMethodType {
        GET, POST
    }

    /**
     * 對(duì)外調(diào)用的Get锈嫩，Post請(qǐng)求
     */
    public void get(String url, IBaseCallBack callBack) {
        Request request = buildRequest(
                url,
                null,
                HttpMethodType.GET);

        doRequest(request, callBack);
    }

    public void post(String url, Map<String, String> parameter,
                     IBaseCallBack callBack) {

        Request request = buildRequest(
                url,
                parameter,
                HttpMethodType.POST);

        doRequest(request, callBack);
    }

    /**
     * 構(gòu)建Get或Post請(qǐng)求的Request
     *
     * @param url        Url地址
     * @param parameter  Post請(qǐng)求所需要的參數(shù)
     * @param methodType 通過(guò)枚舉來(lái)判斷是Get還是Post
     * @return Request
     */
    private Request buildRequest(String url,
                                 Map<String, String> parameter,
                                 HttpMethodType methodType) {

        Request.Builder builder = new Request.Builder();
        builder.url(url);
        if (methodType == HttpMethodType.GET) {
            builder.get();
        } else {
            //構(gòu)建參數(shù)獲取
            RequestBody body = buildFormData(parameter);
            builder.post(body);
        }
        return builder.build();
    }

    /**
     * 構(gòu)建Post請(qǐng)求的body
     */
    private RequestBody buildFormData(Map<String, String> parameter) {
        FormBody.Builder body = new FormBody.Builder();

        if (null != parameter) {

            for (Map.Entry<String, String> entry : parameter.entrySet()) {

                body.add(entry.getKey(), entry.getValue());
            }
        }
        return body.build();
    }


    /**
     * 通過(guò)構(gòu)建好的Get或Post請(qǐng)求的Request受楼，做網(wǎng)絡(luò)訪問(wèn)
     */
    private void doRequest(final Request request, final IBaseCallBack callBack) {

        callBack.onRequestBefore();

        mOkHttpClient.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                requestFailure(callBack, call, e);
            }

            @Override
            public void onResponse(Call call, Response response)
                    throws IOException {

                if (response.isSuccessful()) {
                    String resultStr = response.body().string();

                    if (callBack.mType == String.class) {

                        requestSuccess(callBack, response, request);

                    } else {

                        try {
                            //防止Json解析錯(cuò)誤
                            Object obj = mGson.fromJson(resultStr, callBack.mType);

                            requestSuccess(callBack, response, obj);

                        } catch (JsonParseException e) {
                            requestFailure(callBack, call, e);
                        }
                    }
                } else {
                    requestFailure(callBack, call, null);
                }
            }
        });
    }

    private void requestFailure(final IBaseCallBack callBack,
                                final Call call,
                                final Exception e) {
        mHandler.post(new Runnable() {
            @Override
            public void run() {
                callBack.onFailure(call, e);
            }
        });
    }

    private void requestSuccess(final IBaseCallBack callBack,
                                final Response response,
                                final Object o) {
        mHandler.post(new Runnable() {
            @Override
            public void run() {
                callBack.onSuccess(response, o);
            }
        });
    }
}

3.  設(shè)置接口的包裝類，幫助簡(jiǎn)化不必要的實(shí)現(xiàn)接口或者添加其他方法
注意：兩者同樣是抽象類呼寸，SpotsCallBack重寫(xiě)的抽象方法艳汽，在其子類是不會(huì)主動(dòng)提示覆蓋的

public abstract class SpotsCallBack<T> extends IBaseCallBack<T> {

    ProgressDialog mDialog;

    public SpotsCallBack(Context context) {
        mDialog = new ProgressDialog(context);
        mDialog.setCancelable(false);
        mDialog.setCanceledOnTouchOutside(false);
    }

    public void showDialog() {
        mDialog.show();
    }

    public void dismissDialog() {
        mDialog.dismiss();
    }

    @Override
    public void onRequestBefore() {
        showDialog();
    }
}

具體調(diào)用

private void getUserInfo() {

        HashMap<String, String> paramester = new HashMap<>();
        paramester.put("userName", getUserName());
        paramester.put("userCode", getUserCode());

        OkHttpHelper.getOkHttpHelperInstance()
                .post(requestUrl(), paramester, new SpotsCallBack<User>(this) {
                    @Override
                    public void onSuccess(Response response, User user) {
                        dismissDialog();
                        showUserInfo(user);
                    }

                    @Override
                    public void onFailure(Call call, Exception e) {
                        dismissDialog();
                    }
          });
}