Android中常用的应用都会大量使用网络，比如QQ、微信、访问网页等等。通过使用网络，可以展示网页，发起Http请求获取数据或提交数据。

WebView控件

有时我们可能需要让我们自己的应用展示网页，我们可以使用Android内置的控件WebView。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("http://www.baidu.com");

}

}

布局文件：<?xml version="1.0" encoding="utf-8"?>

android:orientation="vertical"

android:layout_width="match_parent"

android:layout_height="match_parent">

android:id="@+id/web_view"

android:layout_width="match_parent"

android:layout_height="match_parent" />

由于使用了网络功能，需要声明网络权限。在AndroidManifest.xml添加android.permission.INTERNET:<?xml version="1.0" encoding="utf-8"?>

package="com.jyoryo.app.android.study">

android:allowBackup="true"

android:icon="@mipmap/ic_launcher"

android:label="@string/app_name"

android:roundIcon="@mipmap/ic_launcher_round"

android:supportsRtl="true"

android:theme="@style/AppTheme">

Android主线程、子线程主线程，不允许在主线程中进行网络请求，如果需要发起网络请求，方法是开启一个线程，然后在子线程里使用HttpURLConnection发起HTTP请求。例如下面使用HttpURLConnection发起HTTP请求。

子线程，不允许在子线程中进行UI操作，如果需要进行UI操作必须切换到主线程中。可以使用runOnUiThread()方法将线程切换到主线程。

使用runOnUiThread()：private void showResponse(final String response) {

runOnUiThread(new Runnable() {

@Override

public void run() {

responseText.setText(response);

}

});

}

HttpURLConnection

HttpURLConnection是jdk自带的访问网络方式。private void sendRequestWithHttpURLConnection(final String strUrl) {

new Thread(new Runnable() {

@Override

public void run() {

Log.d(TAG, "run: start http request");

HttpURLConnection connection = null;

BufferedReader reader = null;

try {

URL url = new URL(strUrl);

connection = (HttpURLConnection)url.openConnection();

connection.setRequestMethod("GET");

connection.setConnectTimeout(8000);

connection.setReadTimeout(8000);

InputStream in = connection.getInputStream();

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

StringBuilder sbd = new StringBuilder();

String line = null;

while (null != (line = reader.readLine())) {

sbd.append(line);

}

showResponse(sbd.toString());

} catch (Exception e) {

e.printStackTrace();

} finally {

try {

if(null != reader) {

reader.close();

}

if(null != connection) {

connection.disconnect();

}

} catch (Exception e) {

e.printStackTrace();

}

}

}

}).start();

}

如果使用POST方式，比如提交用户名、密码：connection.setRequestMethod("POST");

DataOutputStream out = new DataOutputStream(connection.getOutputStream());

out.writeBytes("username=user&password=123");

OkHttp

通过HttpURLConnection可以完成网络请求，但是比较原始，我们可以通过使用OkHttp更便捷的完成网络请求。private void sendRequestWithOkHttp(final String url) {

new Thread(new Runnable() {

@Override

public void run() {

OkHttpClient client = new OkHttpClient();

Request request = new Request.Builder()

.url(url)

.build();

try {

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

String responseData = response.body().string();

showResponse(responseData);

} catch (Exception e) {

e.printStackTrace();

}

}

}).start();

}

网络请求封装

HttpUtil网络请求封装类：public class HttpUtil {

public interface HttpCallbackListener {

void onFinish(String response);

void onError(Exception e);

}

/**

* HttpURLConnection封装

* @param address

* @param listener

*/

public static void sendHttpRequest(final String address, final HttpCallbackListener listener) {

new Thread(new Runnable() {

@Override

public void run() {

HttpURLConnection connection = null;

try {

URL url = new URL(address);

connection = (HttpURLConnection)url.openConnection();

connection.setConnectTimeout(30000);

connection.setReadTimeout(30000);

connection.setDoInput(true);

connection.setDoOutput(true);

InputStream in = connection.getInputStream();

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

StringBuilder sbd = new StringBuilder();

String line = null;

while (null != (line = reader.readLine())) {

sbd.append(line);

}

// return sbd.toString();

if(null != listener) {

listener.onFinish(sbd.toString());

}

} catch (Exception e) {

e.printStackTrace();

// return e.getMessage();

if(null != listener) {

listener.onError(e);

}

} finally {

if (null != connection) {

connection.disconnect();

}

}

}

}).start();

}

/**

* OkHttpClient封装

* @param address

* @param callback

*/

public static void sendOkHttpRequest(final String address, Callback callback) {

OkHttpClient client = new OkHttpClient();

Request request = new Request.Builder().url(address).build();

client.newCall(request).enqueue(callback);

}

}

HttpUtil使用：/**

* HttpURLConnection方式

*/

HttpUtil.sendHttpRequest(url, new HttpUtil.HttpCallbackListener() {

@Override

public void onFinish(String response) {

showResponse(response);

}

@Override

public void onError(Exception e) {

e.printStackTrace();

}

});

/**

* OkHttp方式

*/

HttpUtil.sendOkHttpRequest(url, new Callback() {

@Override

public void onFailure(Call call, IOException e) {

e.printStackTrace();

}

@Override

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

showResponse(response.body().string());

}

});