使用網路技術

??本章主要講述如何在手機端使用HTTP和服務器進行網路互動,并對服務器回傳的資料進行決議,這也是Android中最常使用到的網路技術

01 WebView的用法

??WebView控制元件,借助它我們就可以在自己的應用程式里嵌入一個瀏覽器,從而非常輕松地展示各種各樣的網頁，

//需在manifest.xml檔案中添加
//application屬性:android:usesCleartextTraffic="true"
//權限<uses-permission android:name="android.permission.INTERNET" />.
//使用百度進行搜索后會有net:err_unknown_url_scheme錯誤
WebView webView = (WebView) findViewById(R.id.webView);
//讓其支持JavaScript腳本
webView.getSettings().setJavaScriptEnabled(true);
webView.setWebViewClient(new WebViewClient());
webView.loadUrl("http://www.baidu.com");

權限允許
<uses-permission android:name="android.permission.INTERNET" />

在manifest.xml中添加application的屬性
<application
    android:usesCleartextTraffic="true"
/>

02 使用HTTP協議訪問網路

??作業原理特別簡單,就是客戶端向服務器發出一條HTTP請求,服務器收到請求之后會回傳一些資料給客戶端,然后客戶端再對這些資料進行決議和處理.

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

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

        //發送http請求
        Button sendHttp = (Button) findViewById(R.id.sendHttp);
        sendHttp.setOnClickListener(this);

        responseText = (TextView) findViewById(R.id.responseText);


    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.sendHttp){
            sendRequestWithHttpURLConnection();
        }
    }

    private void sendRequestWithHttpURLConnection() {
        //1 開啟執行緒發起網路請求
        new Thread(new Runnable() {
            @Override
            public void run() {
                HttpURLConnection connection = null;
                BufferedReader reader = null;

                try {
                    //2 獲取鏈接
                    URL url = new URL("https://www.baidu.com");
                    connection = (HttpURLConnection) url.openConnection();
                    //3 鏈接設定
                    connection.setRequestMethod("GET");
                    connection.setConnectTimeout(8000);
                    connection.setReadTimeout(8000);
                    //4 對獲取到的輸入流進行讀取
                    InputStream in = connection.getInputStream();
                    reader = new BufferedReader(new InputStreamReader(in));
                    StringBuilder response = new StringBuilder();
                    String line;
                    while ((line = reader.readLine()) != null){
                        response.append(line);
                    }
                    showResponse(response.toString());
                } catch (Exception e) {
                    e.printStackTrace();
                }finally {
                    if (reader != null){
                        try {
                            reader.close();
                        }catch (IOException e){
                            e.printStackTrace();
                        }
                    }
                    if (connection != null){
                        connection.disconnect();
                    }
                }


            }
        }).start();

    }

    private void showResponse(final String response) {
        //5 通過runOnUiThread在主執行緒進行UI操作
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                //在這里進行UI操作
                responseText.setText(response);
            }
        });
    }
}

權限

<uses-permission android:name="android.permission.INTERNET" />

03 使用OkHttp

匯入依賴

implementation 'com.squareup.okhttp3:okhttp:4.1.0'

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

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

        //發送http請求
        Button sendHttp = (Button) findViewById(R.id.sendHttp);
        sendHttp.setOnClickListener(this);

        responseText = (TextView) findViewById(R.id.responseText);


    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.sendHttp){
            sendRequestWithOkHttp();
        }
    }

    private void sendRequestWithOkHttp() {
        //1 開啟執行緒發起網路請求
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //2 獲得鏈接
                    OkHttpClient client = new OkHttpClient();
                    Request request = new Request.Builder().
                            url("http://www.baidu.com")
                            .build();
                    //3 接收結果
                    Response response = client.newCall(request).execute();
                    String responseData = response.body().string();
                    showResponse(responseData);
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }
        }).start();

    }

    private void showResponse(final String response) {
        //4 通過runOnUiThread在主執行緒進行UI操作
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                //在這里進行UI操作
                responseText.setText(response);
            }
        });
    }
}

04 決議XML資料-PULL

Ubuntu下安裝apche

sudo apt-get install apache2  //其他配置自行設定

在var/www/html下建立get_data.xml

<apps>
	<app>
		<id>1</id>
		<name>google maps</name>
		<version>1.0</version>
	</app>
</apps>

新建xml/network_config.xml讓程式允許http

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
    <base-config cleartextTrafficPermitted="true">
        <trust-anchors>
            <certificates src="system" />
        </trust-anchors>
    </base-config>
</network-security-config>

manifest中application屬性添加

android:networkSecurityConfig="@xml/network_config

private void sendRequestWithOkHttp() {
    //1 開啟執行緒發起網路請求
    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                //2 獲得鏈接
                OkHttpClient client = new OkHttpClient();
                Request request = new Request.Builder().
                        url("http://10.92.36.25/get_data.xml") //網址10.0.2.2或者自己的ip地址
                        .build();
                //3 接收結果
                Response response = client.newCall(request).execute();
                String responseData = response.body().string();
                parseXMLWithPull(responseData);
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }).start();

}

//決議xml
private void parseXMLWithPull(String xmlData) {
    //進行決議
    XmlPullParserFactory factory = null;
    try {
        //通過工廠獲得XmlPullParser物件
        factory = XmlPullParserFactory.newInstance();
        XmlPullParser xmlPullParser = factory.newPullParser();
        //setInput將服務器回傳的XML資料進行決議
        xmlPullParser.setInput(new StringReader(xmlData));
        //getEventType()可以得到當前決議事件,然后在一個while回圈中不斷決議
        int eventType = xmlPullParser.getEventType();
        String id = "";
        String name = "";
        String version = "";
        while(eventType != XmlPullParser.END_DOCUMENT){
            String nodeName = xmlPullParser.getName();
            switch (eventType){
                //開始決議節點<>
                case XmlPullParser.START_TAG: {
                    if ("id".equals(nodeName)) {
                        id = xmlPullParser.nextText();
                    } else if ("name".equals(nodeName)) {
                        name = xmlPullParser.nextText();
                    } else if ("version".equals(nodeName)) {
                        version = xmlPullParser.nextText();
                    }
                    break;
                }
                //完成決議某個節點</>
                case XmlPullParser.END_TAG:{
                    if ("app".equals(nodeName)){
                        Log.d(TAG, "id is "+ id);
                        Log.d(TAG, "name is "+ name);
                        Log.d(TAG, "version is "+ version);
                    }
                    break;
                }
                default:
                    break;
            }
            eventType = xmlPullParser.next();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

05 決議XML資料-SAX

新建類繼承DefaultHandler

public class ContentHandler extends DefaultHandler {

    private static final String TAG = "ContentHandler";
    private String nodeName;
    private StringBuilder id;
    private StringBuilder name;
    private StringBuilder version;

    //開始document決議時呼叫
    @Override
    public void startDocument() throws SAXException {
        id = new StringBuilder();
        name = new StringBuilder();
        version = new StringBuilder();
    }

    //開始決議某個節點時呼叫
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        //記錄當前節點名
        nodeName = localName;
    }

    //獲取節點中內容時呼叫
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        //根據當前節點名判斷將內容添加到哪一個stringbuilder物件中
        if ("id".equals(nodeName)) {
            id.append(ch,start,length);
        } else if ("name".equals(nodeName)) {
            name.append(ch,start,length);
        } else if ("version".equals(nodeName)) {
            version.append(ch,start,length);
        }
    }

    //完成決議某個節點時呼叫
    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if ("app".equals(localName)){
            Log.d(TAG, "id is "+ id.toString().trim());
            Log.d(TAG, "name is "+ name.toString().trim());
            Log.d(TAG, "version is "+ version.toString().trim());
            id.setLength(0);
            name.setLength(0);
            version.setLength(0);
        }
    }

    //完成整個XML決議時呼叫.
    @Override
    public void endDocument() throws SAXException {
        super.endDocument();
    }
}

MainActivity.java
private void sendRequestWithOkHttp() {
    //1 開啟執行緒發起網路請求
    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                //2 獲得鏈接
                OkHttpClient client = new OkHttpClient();
                Request request = new Request.Builder().
                        url("http://10.92.36.25/get_data.xml") //網址10.0.2.2或者自己的ip地址
                        .build();
                //3 接收結果
                Response response = client.newCall(request).execute();
                String responseData = response.body().string();
                parseXMLWithSAX(responseData);
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }).start();

}

//SAX決議xml
private void parseXMLWithSAX(String xmlData) {
    try {
        SAXParserFactory factory = SAXParserFactory.newInstance();
        XMLReader xmlReader = factory.newSAXParser().getXMLReader();
        ContentHandler handler = new ContentHandler();
        //將contenthandler的實體放到XMLReader中
        xmlReader.setContentHandler(handler);
        xmlReader.parse(new InputSource(new StringReader(xmlData)));
    } catch (Exception e) {
        e.printStackTrace();
    }
}

??首先給id、name和version節點分別定義了一個StringBuilder物件,并在**startDocument()**方法里對它們進行了初始化，每當開始決議某個節點的時候,**startElement()方法就會得到呼叫,其中localName引數記錄著當前節點的名字,這里我們把它記錄下來，接著在決議節點中具體內容的時候就會呼叫characters()方法,我們會根據當前的節點名進行判斷,將決議出的內容添加到哪一個StringBuilder物件中，最后在endElement()**方法中進行判斷,如果app節點已經決議完成,就列印出id、name和version的內容，需要注意的是,目前id、name和version中都可能是包括回車或換行符的,因此在列印之前我們還需要呼叫一下trim()方法,并且列印完成后要將StringBuilder的內容清空,不然的話會影響下一次內容的讀取，

06 決議JSON資料-JSONObject

同樣先在var/www/html(apache默認根目錄)下創建get_data.json

private void sendRequestWithOkHttp() {
    //1 開啟執行緒發起網路請求
    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                //2 獲得鏈接
                OkHttpClient client = new OkHttpClient();
                Request request = new Request.Builder().
                        url("http://10.92.36.25/get_data.json") //網址10.0.2.2或者自己的ip地址
                        .build();
                //3 接收結果
                Response response = client.newCall(request).execute();
                String responseData = response.body().string();
                parseJSONWithJSONObject(responseData);
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }).start();

}

//決議JSON
private void parseJSONWithJSONObject(String jsonData) {
    try {
        JSONArray jsonArray = new JSONArray(jsonData);
        for (int i = 0; i < jsonArray.length(); i++) {
            JSONObject jsonObject = jsonArray.getJSONObject(i);
            String id = jsonObject.getString("id");
            String name = jsonObject.getString("name");
            String version = jsonObject.getString("version");
            Log.d(TAG, "id is "+ id);
            Log.d(TAG, "name is "+ name);
            Log.d(TAG, "version is "+ version);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

07 決議JSON資料-GSON

<!--添加依賴-->
implementation 'com.google.code.gson:gson:2.8.5'

private void sendRequestWithOkHttp() {
    //1 開啟執行緒發起網路請求
    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                //2 獲得鏈接
                OkHttpClient client = new OkHttpClient();
                Request request = new Request.Builder().
                        url("http://10.92.36.25/get_data.json") //網址10.0.2.2或者自己的ip地址
                        .build();
                //3 接收結果
                Response response = client.newCall(request).execute();
                String responseData = response.body().string();
                parseJSONWithGSON(responseData);
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }).start();

}

//決議JSON
private void parseJSONWithGSON(String jsonData) {
    try {
        Gson gson = new Gson();
        List<App> appList = gson.fromJson(jsonData,new TypeToken< List<App> >(){}.getType() );
        for (App app : appList){
            Log.d(TAG, "id is "+ app.getId());
            Log.d(TAG, "name is "+ app.getName());
            Log.d(TAG, "version is "+ app.getVersion());
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

得新建一個類用于映射

public class App {
    private String id;
    private String name;
    private String version;

    public void setId(String id) {
        this.id = id;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setVersion(String version) {
        this.version = version;
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getVersion() {
        return version;
    }
}

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Android學習筆記-使用網路技術