新建一个项目, 修改 activity_main.xml, 添加一个 WebView :
<RelativeLayout 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"/>
RelativeLayout>
修改 MainActivity :
public class MainActivity extends Activity {
private WebView webView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
webView = (WebView) findViewById(R.id.web_view);
//设置一些浏览器的属性, 让 WebView 支持 JavaScript 脚本
webView.getSettings().setJavaScriptEnabled(true);
//表明当需要从一个网页跳转到另一个网页时, 仍然在当前 WebView 中打开
webView.setWebViewClient(new WebViewClient(){
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
view.loadUrl(url);//根据传入的参数再去加载新的网页
return true;//表示当前 WebView 可以处理打开新网页的请求, 不用借助系统浏览器
}
});
webView.loadUrl("http://www.baidu.com");
}
}
最后, 由于使用了网络, 申请权限:
HTTP 协议工作原理:
客户端向服务器发送一条 HTTP 请求, 服务器收到请求后返回一些数据给客户端, 客户端再对这些数据进行解析和处理.
浏览器工作流程: 发送 HTTP 请求–> 接受服务响应–> 解析返回数据–> 页面展示
流程:
获取到 HttpURLConnection 实例–> 设置 HTTP 请求方法–> 自由设置(连接超时读取超时等)–> 获取到返回的输入流–> 关闭连接
新建一个项目, 修改 activity_main.xml
<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="wrap_content"
android:text="Send Request" />
<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>
注:
, 允许以滚动的形式查看屏幕外的内容.
修改 MainActivity:
public class MainActivity extends Activity implements View.OnClickListener {
public static final int SHOW_RESPONSE = 0;
private Button sendRequest;
private TextView responseText;
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case SHOW_RESPONSE:
String response = (String) msg.obj;
responseText.setText(response);
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
sendRequest = (Button) findViewById(R.id.send_request);
responseText = (TextView) findViewById(R.id.response_text);
sendRequest.setOnClickListener(this);
}
@Override
public void onClick(View v) {
if (v.getId() == R.id.send_request) {
sendRequestWithHttpURLConnection();
}
}
private void sendRequestWithHttpURLConnection() {
//开启线程发起网络请求
new Thread(new Runnable() {
@Override
public void run() {
HttpURLConnection connection = null;
try {
URL url = new URL("http://www.baidu.com");
connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setConnectTimeout(8000);
connection.setReadTimeout(8000);
InputStream in = connection.getInputStream();
//读取输入流
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
StringBuilder response = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
response.append(line);
}
Message message = new Message();
message.what = SHOW_RESPONSE;
message.obj = response.toString();
handler.sendMessage(message);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (connection != null) {
connection.disconnect();
}
}
}
}).start();
}
}
最后添加权限.
运行程序, 可以看到返回的是 HTML 代码.
在刚才创建的项目中的 MainActivity 类中添加一个方法:
private void sendRequestWithHttpClient() {
new Thread(new Runnable() {
@Override
public void run() {
try {
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet("http://www.baidu.com");
HttpResponse httpResponse = httpClient.execute(httpGet);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
HttpEntity entity = httpResponse.getEntity();
String response = EntityUtils.toString(entity, "utf-8");//中文防乱码
Message message = new Message();
message.what = SHOW_RESPONSE;
message.obj = response.toString();
handler.sendMessage(message);
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
使用 tomcat 服务器. 自己创建一个 get_data.xml文件, 内容:
<apps>
<app>
<id>1id>
<name>Google Mapname>
<version>1.0version>
app>
<app>
<id>2id>
<name>Chromename>
<version>2.1version>
app>
<app>
<id>3id>
<name>Google Playname>
<version>2.3version>
app>
apps>
修改 MainActivity :
public class MainActivity extends Activity implements View.OnClickListener {
...
private void sendRequestWithHttpClient() {
new Thread(new Runnable() {
@Override
public void run() {
try {
HttpClient httpClient = new DefaultHttpClient();
//指定访问的服务器地址是电脑本机(10.0.2.2对于模拟器来说就是电脑本机的IP 地址)
HttpGet httpGet = new HttpGet("http://10.0.2.2/get_data.xml");
HttpResponse httpResponse = httpClient.execute(httpGet);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
HttpEntity entity = httpResponse.getEntity();
String response = EntityUtils.toString(entity, "utf-8");//中文防乱码
//开始进行 Pull 解析
parseXMLWithPull(response);
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
//Pull 解析的具体流程
private void parseXMLWithPull(String xmlData) {
try {
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
XmlPullParser xmlPullParser = factory.newPullParser();
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) {
//开始解析某个节点
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;
}
//完成解析某个节点
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();
}
}
...
}
注意, 把tomcat的端口号修改为80, 才能正常打印出结果.
新建一个类继承自 DefaultHandler:
public class ContentHandler extends DefaultHandler {
private String nodeName;
private StringBuilder id;
private StringBuilder name;
private StringBuilder version;
@Override
public void startDocument() throws SAXException {
id = new StringBuilder();
name = new StringBuilder();
version = new StringBuilder();
}
@Override
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
//记录当前结点名
nodeName = localName;
}
@Override
public void characters(char[] ch, int start, int length) throws SAXException {
//根据当前结点名判断将内容添加到哪一个StringBuilder对象中
if ("id".equals(nodeName)) {
id.append(ch, start, length);
}
else if ("name".equals(nodeName)) {
id.append(ch, start, length);
}
else if ("version".equals(nodeName)) {
id.append(ch, start, length);
}
}
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
if ("app".equals(localName)) {
Log.d("TAG", "id is " + id.toString().trim());//忽略前导空白和尾部空白
Log.d("TAG", "name is " + name.toString().trim());
Log.d("TAG", "version is " + version.toString().trim());
//将 StringBuilder 清空
id.setLength(0);
name.setLength(0);
version.setLength(0);
}
}
@Override
public void endDocument() throws SAXException {
}
}
修改 MainActivity :
public class MainActivity extends Activity implements View.OnClickListener {
...
private void sendRequestWithHttpClient() {
new Thread(new Runnable() {
@Override
public void run() {
try {
HttpClient httpClient = new DefaultHttpClient();
//指定访问的服务器地址是电脑本机(10.0.2.2对于模拟器来说就是电脑本机的IP 地址)
HttpGet httpGet = new HttpGet("http://10.0.2.2/get_data.xml");
HttpResponse httpResponse = httpClient.execute(httpGet);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
HttpEntity entity = httpResponse.getEntity();
String response = EntityUtils.toString(entity, "utf-8");//中文防乱码
//开始进行 Pull 解析
//parseXMLWithPull(response);
//开始进行 SAX 解析
parseXMLWithSAX(response);
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
//SAX 解析具体流程
private void parseXMLWithSAX(String xmlData) {
try {
SAXParserFactory factory = SAXParserFactory.newInstance();
XMLReader xmlReader = factory.newSAXParser().getXMLReader();
ContentHandler handler = new ContentHandler();
//将 ContentHandler 实例设置到 XMLReader 中
xmlReader.setContentHandler(handler);
//开始执行解析
xmlReader.parse(new InputSource(new StringReader(xmlData)));
} catch (Exception e) {
e.printStackTrace();
}
}
...
相比于 XML, JSON格式的主要优势在于它的体积更小, 在网络上传输的时候更省流量. 缺点在于, 它的语义性较差, 看起来不如 XML 直观.
新建一个 get_data.json :
[{"id":"5","version":"5.5","name":"Angry Birds"},
{"id":"6","version":"7.0","name":"Clash of Clans"},
{"id":"7","version":"3.5","name":"Hey Day"}]
修改 MainActivity 的代码:
public class MainActivity extends Activity implements View.OnClickListener {
...
private void sendRequestWithHttpClient() {
new Thread(new Runnable() {
@Override
public void run() {
try {
HttpClient httpClient = new DefaultHttpClient();
//指定访问的服务器地址是电脑本机(10.0.2.2对于模拟器来说就是电脑本机的IP 地址)
HttpGet httpGet = new HttpGet("http://10.0.2.2/get_data.json");
HttpResponse httpResponse = httpClient.execute(httpGet);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
HttpEntity entity = httpResponse.getEntity();
String response = EntityUtils.toString(entity, "utf-8");//中文防乱码
//开始进行 Pull 解析
//parseXMLWithPull(response);
//开始进行 SAX 解析
parseXMLWithSAX(response);
//使用 JSONObject 解析 JSON
parseJSONWithJSONObject(response);
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
// JSONObject 解析具体流程
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();
}
}
...
}
新建一个 App 类:
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;
}
}
修改 MainActivity 的代码:
public class MainActivity extends Activity implements View.OnClickListener {
...
private void sendRequestWithHttpClient() {
new Thread(new Runnable() {
@Override
public void run() {
try {
HttpClient httpClient = new DefaultHttpClient();
//指定访问的服务器地址是电脑本机(10.0.2.2对于模拟器来说就是电脑本机的IP 地址)
HttpGet httpGet = new HttpGet("http://10.0.2.2/get_data.json");
HttpResponse httpResponse = httpClient.execute(httpGet);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
HttpEntity entity = httpResponse.getEntity();
String response = EntityUtils.toString(entity, "utf-8");//中文防乱码
//开始进行 Pull 解析
//parseXMLWithPull(response);
//开始进行 SAX 解析
//parseXMLWithSAX(response);
//使用 JSONObject 解析 JSON
//parseJSONWithJSONObject(response);
//使用 GSON 解析 JSON
parseJSONWithGSON(response);
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
//使用 GSON 解析 JSON
private void parseJSONWithGSON(String jsonData) {
Gson gson = new Gson();
List appList = gson.fromJson(jsonData, new TypeToken>() {}.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());
}
}
...
应该将通用的网络操作提取到一个公共类里, 并提供一个静态方法, 当想要发起网络请求的时候调用一下这个方法就可以.
由于请求网络属于耗时操作, 需要在子线程中进行, 但是子线程无法通过 return 语句来返回数据, 所以使用回调机制来解决这个问题.
首先定义一个接口, 比如命名为 HttpCallbackListener :
public interface HttpCallbackListener {
void onFinish(String response);
void onError(Exception e);
}
该接口定义两个方法, onFinish()
在请求成功时候调用, 其参数代表服务器返回的数据. onError()
在请求失败时候调用, 其参数记录着错误的详细信息.
然后新建一个类, HttpUtil:
public class HttpUtil {
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.setRequestMethod("GET");
connection.setConnectTimeout(8000);
connection.setReadTimeout(8000);
connection.setDoInput(true);
connection.setDoOutput(true);
InputStream in = connection.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
StringBuilder response = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
response.append(line);
}
if (listener != null) {
//回调 onFinish() 方法
listener.onFinish(response.toString());
}
} catch (Exception e) {
if (listener != null) {
//回调 onError() 方法
listener.onError(e);
}
} finally {
if (connection != null) {
connection.disconnect();
}
}
}
}).start();
}
}
在调用这个类的静态方法时, 只需:
String address = "http://www.baidu.com";
HttpUtil.sendHttpRequest(address, new HttpCallbackListener() {
@Override
public void onFinish(String response) {
//在这里柑橘返回内容执行具体逻辑
}
@Override
public void onError(Exception e) {
//在这里对异常进行处理
}
});