Android初級開發（九）——網絡交互—OkHttp

一、使用OkHttp的步驟
1、在項目中添加OkHttp庫的依賴
在File->Project Structure->app->Dependencies->+（添加）->搜索OkHttp->找“com.squareup.okhttp3:okhttp:3.8.1”確定添加

2、首先創建OkHttpClient實例

OkHttpClient client = new OkHttpClient();

3、發送GET請求或POST請求
GET請求：創建一個request對象，並在build()前連綴很多方法來豐富這個request對象

Request request = new Request.Builder().url("http://www.baidu.com").build();

POST請求：先構建body對象存放數據，然後在Request.Builder()調用post方法將body對象傳入

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();

4、調用execute（）方法發送請求並獲取服務器返回的數據

Response response = client.newCall(request).execute();

二、實現一下吧
1、效果圖
效果圖和上一篇HttpURLConnection的使用中的是一樣的，因爲發送都是訪問百度頁面的請求

2、佈局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <Button
        android:id="@+id/send_request"
        android:layout_width="match_parent"
        android:layout_height="80dp"
        android:text="發送請求"
        android:textSize="25dp"/>
    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <TextView
            android:id="@+id/response_text"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </ScrollView>


</LinearLayout>

3、MainActivity.java

public class MainActivity extends AppCompatActivity {

    Button sendRequest;
    TextView responseText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        responseText = (TextView) findViewById(R.id.response_text);
        sendRequest = (Button) findViewById(send_request);
        sendRequest.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try{
                            OkHttpClient client = new OkHttpClient();
                            Request request = new Request.Builder().url("http://www.baidu.com").build();
                            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) {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                //在這裏進行UI操作，將結果顯示到界面上
                responseText.setText(response);
            }
        });
    }

}

4、在清單文件中聲明網絡權限

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