Android开发学习之路--网络编程之初体验

    一般手机都是需要上网的，一般我们的浏览器就是个webview。这里简单实现下下功能，先编写Android的layout布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:layout_margin="10dp"
    android:padding="10dp"
    tools:context="com.example.jared.webviewstudy.MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <EditText
            android:id="@+id/netAddress"
            android:layout_weight="1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
        <Button
            android:id="@+id/openNetAddress"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:layout_weight="0"
            android:text="Open"
            android:textAllCaps="false"/>
    </LinearLayout>

    <WebView
        android:id="@+id/webView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

    这里主要是一个EditText用来输入网址，然后一个Button用来打开网页，webView用来呈现网页。编写代码如下：

package com.example.jared.webviewstudy;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity {

    private WebView myWebView;
    private EditText networkAddr;
    private Button openNetwork;

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

        networkAddr = (EditText)findViewById(R.id.netAddress);
        myWebView = (WebView)findViewById(R.id.webView);

        openNetwork = (Button)findViewById(R.id.openNetAddress);
        openNetwork.setOnClickListener(new myOnClickListener());
    }

    class myOnClickListener implements View.OnClickListener {
        @Override
        public void onClick(View view) {
            myWebView.getSettings().setJavaScriptEnabled(true);
            myWebView.setWebViewClient(new WebViewClient() {
                @Override
                public boolean shouldOverrideUrlLoading(WebView view, String url) {
                    view.loadUrl(url);
                    return true;
                }
            });
            String networkAddress = networkAddr.getText().toString();
            myWebView.loadUrl("http://"+networkAddress);
        }
    }
}

    还有就是权限问题了：

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

    这里通过setWebViewClient方法，实例化一个WebViewClient，loadurl实现网页的加载。运行看下效果：

   

    这里打开了百度和我的博客的地址，界面略难看，勉强看看了。

    一般网络编程都是通过http的，下面就来实现下，首先是HttpURLConnection，这个一般是google官方提供的，还有一个HttpClient，本来有的，现在api23也没有了，需要自己加载进来。

    先使用HttpURLConnection和HttpClient吧，新建工程，编写layout代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:layout_margin="10dp"
    tools:context="com.example.jared.httpurlconnectionstudy.MainActivity">

    <Button
        android:id="@+id/sendRequest"
        android:text="发送请求"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
        <TextView
            android:id="@+id/response"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </ScrollView>

</LinearLayout>

    这里主要就是一个按钮获取数据，然后http请求的数据通过ScrollView可以滑动浏览更多的信息，然后把获取到的信息显示在TextView里面。

    编写MainActivity，里面有实现了HttpURLConnection和HttpClient：

package com.example.jared.httpurlconnectionstudy;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MainActivity extends AppCompatActivity {

    private static final int SHOW_RESPONSE = 1;

    private Button sendRequestBtn;
    private TextView responseView;

    private Handler mHandler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case SHOW_RESPONSE:
                    String responseContent = (String)msg.obj;
                    responseView.setText(responseContent);
                    break;
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActionBar actionBar = getSupportActionBar();
        actionBar.hide();

        setContentView(R.layout.activity_main);

        responseView = (TextView)findViewById(R.id.response);
        sendRequestBtn = (Button)findViewById(R.id.sendRequest);
        sendRequestBtn.setOnClickListener(new myOnClickListener());

    }

    private class myOnClickListener implements View.OnClickListener {
        @Override
        public void onClick(View view) {
            switch (view.getId()) {
                case R.id.sendRequest:
                    String url = "http://www.baidu.com";
                    //sendRequestWithHttpURLConnection(url);
                    sendRequestWithHttpClient(url);
                    break;
                default:
                    break;
            }
        }
    }

    private void sendRequestWithHttpClient(final String url) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    HttpClient httpClient = new DefaultHttpClient();
                    HttpGet httpGet = new HttpGet(url);
                    HttpResponse httpResponse = httpClient.execute(httpGet);
                    if(httpResponse.getStatusLine().getStatusCode() == 200) {
                        HttpEntity entity = httpResponse.getEntity();
                        String response = EntityUtils.toString(entity, "utf-8");

                        Message message = new Message();
                        message.what = SHOW_RESPONSE;
                        message.obj = response.toString();
                        mHandler.sendMessage(message);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

    private void sendRequestWithHttpURLConnection(final String url) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                HttpURLConnection connection = null;
                try {
                    URL mUrl = new URL(url);
                    connection = (HttpURLConnection)mUrl.openConnection();
                    connection.setRequestMethod("GET");
                    connection.setConnectTimeout(8000);
                    connection.setReadTimeout(8000);
                    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);
                    }
                    Message message = new Message();
                    message.what = SHOW_RESPONSE;
                    message.obj = response.toString();
                    mHandler.sendMessage(message);
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (connection != null) {
                        connection.disconnect();
                    }
                }
            }
        }).start();
    }
}

    这里的HttpClient需要在\sdk\platforms\android-23\optional下倒入包到工程目录的libs下面，然后

在build.gradle下面添加

// Apache Http
android {
    useLibrary 'org.apache.http.legacy'
}
// Header
dependencies {
    compile "org.apache.httpcomponents:httpcore:4.3.2"
}

    这样HttpClient就可以使用了，关于加载别的库，也基本上类似了。

   运行效果如下：

    关于Http常用的框架有android-async-http，下面就使用下。jar包可以从官网下载：http://loopj.com/android-async-http/。此外还得下载一个httpclient的jar包：http://mvnrepository.com/artifact/cz.msebera.android/httpclient/4.4.1.1。

    修改build.gradle如下：

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.1'
    compile files('libs/android-async-http-1.4.9.jar')
    compile files('libs/httpclient-4.4.1.1.jar')
}

这里把两个包都放在了libs的目录下。切换到project目录，如下图：

    修改MainActivity代码，添加sendRequestWithAsyncHttpClinet方法如下：

private void sendRequestWithAsyncHttpClient(String url) {
        AsyncHttpClient client = new AsyncHttpClient();
        client.get(url, new AsyncHttpResponseHandler() {
            @Override
            public void onSuccess(int i, Header[] headers, byte[] bytes) {
                try {
                    String response = new String(bytes, 0, bytes.length, "UTF-8");
                    responseView.setText(response);
                }catch (Exception e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void onFailure(int i, Header[] headers, byte[] bytes, Throwable throwable) {

            }
        });
    }

    运行可以得到我们一样的效果。AsyncHttpClient很方便地可以使用起来了，比起上面一大堆代码简单了不少。这里通过一个get方法，然后再onSuccess方法中把获取到的数据转为String显示在text就ok了。

    关于网络编程的webview和http就基本学到这里了。在此还要谢谢朋友的提醒，光学基础，实际项目会用到很多框架的，需要去熟悉，这里继续慢慢学。