《第一行代碼》 第九章：使用網絡技術

一，WebView的用法

活動布局的代碼：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <WebView
        android:id="@+id/web_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>
           

然後在活動頁中修改代碼：

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        WebView webView=(WebView) findViewById(R.id.web_view);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.setWebViewClient(
                new WebViewClient()
        );
        webView.loadUrl("https://www.baidu.com");
    }
}
           

menifest檔案中增權重限控制

二，使用http協定通路網絡

1，使用OkHttpClient

第一步：在app/build.gradle檔案中引入庫

implementation 'com.squareup.okhttp3:okhttp:3.14.7'
    implementation 'com.squareup.okio:okio:1.17.5'
           

第二步：在menifest檔案中申請網絡權限

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

第三步：布局修改

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <TextView
            android:id="@+id/test_text"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
    </ScrollView>
</LinearLayout>
           

第四步：活動頁中修改發起get請求

public class MainActivity extends AppCompatActivity {
    TextView responseText;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
         responseText=(TextView) findViewById(R.id.test_text);
        //建立一個OkHttpClient執行個體
        OkHttpClient httpClient = new OkHttpClient();
        String url = "https://www.baidu.com/";
        //建構一個request對象
        Request getRequest = new Request.Builder()
                .url(url)
                .get()
                .build();
        //調用OkHttpClient建立一個Call對象
        Call call = httpClient.newCall(getRequest);
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //同步請求，要放到子線程執行，調用它的execute方法發送請求
                    Response response = call.execute();
                   //将内容顯示到桌面上
                    showResponse(response.body().string());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
    private void showResponse(final String response){
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                responseText.setText(response);
            }
        });
    }
}
           

2，如果是post請求的話，就需要是這樣：

//建立一個OkHttpClient執行個體
        OkHttpClient httpClient = new OkHttpClient();
        RequestBody requestBody=new FormBody.Builder()
                .add("username","admin")
                .add("password","123456")
                .build();
        Request request=new Request.Builder()
                .url("http://www.baidu.com")
                .post(requestBody)
                .build();
        //調用OkHttpClient建立一個Call對象
        Call call = httpClient.newCall(request);
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //同步請求，要放到子線程執行，調用它的execute方法發送請求
                    Response response = call.execute();
                   //将内容顯示到桌面上
                    showResponse(response.body().string());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
           

三，解析XML格式檔案

在網絡上傳輸的資料通常是有兩種格式XML和JSON.

1,資料從哪裡來

我們可以搭建一個web伺服器，然後在這個伺服器上提供一段XML格式的資料。接着在我們的程式裡面取通路這個伺服器，再對得到的XML文本進行解析。

建立一個get_data.xml檔案：

<apps>
    <app>
        <id>1</id>
        <name>Google maps</name>
        <version>1.0</version>
    </app>
    <app>
        <id>2</id>
        <name>Chrome</name>
        <version>2.1</version>
    </app>
    <app>
        <id>3</id>
        <name>Google Play</name>
        <version>2.3</version>
    </app>
</apps>
           

放置到nginx檔案中（nginx下載下傳使用參考：https://blog.csdn.net/weixin_42349568/article/details/129245335?spm=1001.2014.3001.5501）：

然後浏覽器通路即可得到這個：

2，Pull解析xml

public class MainActivity extends AppCompatActivity {
    TextView responseText;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        responseText=(TextView) findViewById(R.id.test_text);
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //建立一個OkHttpClient執行個體
                    OkHttpClient httpClient = new OkHttpClient();
                    Request request=new Request.Builder()
                            .url("http://172.20.10.8/get_data.xml")
                            .build();
                    //同步請求，要放到子線程執行，調用它的execute方法發送請求
                    Response response = httpClient.newCall(request).execute();
                    String responseData=response.body().string();
                    Log.d("TAG", responseData);
                    parseXMLWithPull(responseData);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
    private String parseXMLWithPull( String xmlData){
        StringBuilder stringBuilder = new StringBuilder();
        try {
            //建立工廠
            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
            //擷取執行個體
            XmlPullParser xmlPullParser = factory.newPullParser();
            //向解析器添加xml資料
            xmlPullParser.setInput(new StringReader(xmlData));
            int eventType = xmlPullParser.getEventType();
            String id = "";
            String name = "";
            String version = "";
            while (eventType != XmlPullParser.END_DOCUMENT) {
                String nodeName = xmlPullParser.getName();
                switch (eventType) {
                    case XmlPullParser.START_TAG: {
                        if ("id".equals(nodeName)) {
                            id = xmlPullParser.nextText();
                            stringBuilder.append("id:" + id + "  ");
                        } else if ("name".equals(nodeName)) {
                            name = xmlPullParser.nextText();
                            stringBuilder.append("name:" + name + "  ");
                        } else if("version".equals(nodeName)){
                            version = xmlPullParser.nextText();
                            stringBuilder.append("version:" + version + "  ");
                        }
                        break;
                    }
                    case XmlPullParser.END_TAG: {
                        stringBuilder.append("\n");
                        break;
                    }
                    default:
                }
                try {
                    eventType = xmlPullParser.next();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("result:\n" + stringBuilder.toString());
        return stringBuilder.toString();
    }
}
           

中間如果遇到了網絡通路有問題的情況，可以參考這篇部落格：https://blog.csdn.net/java558/article/details/111357872。

實作的效果：

四，解析JSON格式檔案

1，建立json檔案

[{"id":"5","version":"5.5","name":"clash of class"},
{"id":"6","version":"7.2","name":"clash of class"},
{"id":"7","version":"8.3","name":"clash of class"}]
           

2，使用GSON來解析json

第一步：引入依賴：

第二步：建立app類

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

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getVersion() {
        return 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;
    }
}

           

第三步：實作解析

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //建立一個OkHttpClient執行個體
                    OkHttpClient httpClient = new OkHttpClient();
                    Request request=new Request.Builder()
                            .url("http://172.20.10.8/get_data.json")
                            .build();
                    //同步請求，要放到子線程執行，調用它的execute方法發送請求
                    Response response = httpClient.newCall(request).execute();
                    String responseData=response.body().string();
                    parseJSONWithGSON(responseData);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
    private void parseJSONWithGSON(String jsonData){
        Gson gson=new Gson();
        List<App> appList=gson.fromJson(jsonData,new TypeToken<List<App>>(){}.getType());
        for (int i=0;i<appList.size();i++){
            App app=appList.get(i);
            String name = app.getName();

            Log.d("TAG", name);
        }
    }
}