Android开发学习之路--网络编程之初体验

2022-11-05 18:01:15

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。

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