示例
下面的示例演示HttpURLConnection类的用法。它创建一个基本的应用程序，使您可以从给定的网页下载HTML。要试验此示例，您需要在连接了wifi互联网的实际设备上运行该示例。
- 您将使用Android Studio创建一个Android应用程序，并将其命名为Demo，位于com.jc2182.demo包下，如Hello World示例一章中所述。
- 修改src/MainActivity.java文件以添加活动代码。
- 修改布局XML文件res/layout/activity_main.xml如果需要，可添加任何GUI组件。
- 修改AndroidManifest.xml以添加必要的权限。
- 运行该应用程序以启动Android模拟器并验证在该应用程序中所做更改的结果。
以下是修改后的主要活动文件src/com.jc2182.demo/MainActivity.java的内容。
package com.jc2182.demo;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
public class MainActivity extends Activity {
private ProgressDialog progressDialog;
private Bitmap bitmap = null;
Button b1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1 = (Button) findViewById(R.id.button);
boolean isConnect = checkInternetConnection(this);
if (!isConnect){
// todo
}
b1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
downloadImage("https://www.cainiaoya.com/wp-content/themes/wiki/images/logo.png");
}
});
}
private void downloadImage(String urlStr) {
progressDialog = ProgressDialog.show(this, "", "从：" + urlStr + "下载图片");
final String url = urlStr;
new Thread() {
public void run() {
InputStream in = null;
Message msg = Message.obtain();
msg.what = 1;
try {
in = openHttpConnection(url);
bitmap = BitmapFactory.decodeStream(in);
Bundle b = new Bundle();
b.putParcelable("bitmap", bitmap);
msg.setData(b);
in.close();
}catch (IOException e1) {
e1.printStackTrace();
}
messageHandler.sendMessage(msg);
}
}.start();
}
private InputStream openHttpConnection(String urlStr) {
InputStream in = null;
int resCode = -1;
try {
URL url = new URL(urlStr);
URLConnection urlConn = url.openConnection();
if (!(urlConn instanceof HttpURLConnection)) {
throw new IOException("URL不是Http URL");
}
HttpURLConnection httpConn = (HttpURLConnection) urlConn;
httpConn.setAllowUserInteraction(false);
httpConn.setInstanceFollowRedirects(true);
httpConn.setRequestMethod("GET");
httpConn.connect();
resCode = httpConn.getResponseCode();
if (resCode == HttpURLConnection.HTTP_OK) {
in = httpConn.getInputStream();
}
}catch (MalformedURLException e) {
e.printStackTrace();
}catch (IOException e) {
e.printStackTrace();
}
return in;
}
private Handler messageHandler = new Handler() {
public void handleMessage(Message msg) {
super.handleMessage(msg);
ImageView img = (ImageView) findViewById(R.id.imageView);
img.setImageBitmap((Bitmap) (msg.getData().getParcelable("bitmap")));
progressDialog.dismiss();
}
};
private boolean checkInternetConnection(Context context) {
try {
ConnectivityManager connectivity = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
if (connectivity != null) {
NetworkInfo info = connectivity.getActiveNetworkInfo();
if (info != null) {
if (info.getState() == NetworkInfo.State.CONNECTED && info.getType() == ConnectivityManager.TYPE_WIFI) {
Toast.makeText(context,"WIFI 已经连接",Toast.LENGTH_SHORT).show();
return true;
}
if (info.getState() == NetworkInfo.State.CONNECTED && info.getType() == ConnectivityManager.TYPE_MOBILE) {
Toast.makeText(context,"移动数据 已经连接",Toast.LENGTH_SHORT).show();
return true;
}
}
}
} catch (Exception e) {
return false;
}
return false;
}
}
以下是res/layout/activity_main.xml文件的内容-
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
tools:context=".MainActivity">
<TextView
android:id="@+id/textView"
android:layout_width="300dp"
android:layout_height="68dp"
android:layout_centerHorizontal="true"
android:text="网络连接例子"
android:textSize="25sp" />
<TextView
android:id="@+id/textView2"
android:layout_width="311dp"
android:layout_height="wrap_content"
android:layout_below="@+id/textView"
android:layout_alignEnd="@+id/textView"
android:layout_alignRight="@+id/textView"
android:layout_marginTop="9dp"
android:text="菜鸟教程"
android:textColor="#ff36ff15"
android:textIsSelectable="false"
android:textSize="35dp" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/imageView"
android:layout_below="@+id/textView2"
android:layout_centerHorizontal="true" />
<Button
android:id="@+id/button"
android:layout_width="161dp"
android:layout_height="wrap_content"
android:layout_below="@+id/imageView"
android:layout_centerHorizontal="true"
android:layout_marginTop="9dp"
android:text="按钮" />
</RelativeLayout>
以下是AndroidManifest.xml文件的内容-
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.jc2182.demo">
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:usesCleartextTraffic="true"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".SecondMain"></activity>
</application>
</manifest>
让我们尝试运行刚刚修改的应用程序。我假设您在进行环境设置时已创建了AVD。要从Android Studio运行该应用，请打开您项目的活动文件之一，然后工具栏中单击“运行”图标。Android studio将应用程序安装在您的AVD上并启动它，如果设置和应用程序一切正常，它将显示在“模拟器”窗口下面-
点击按钮，将下载logo图片到我们的界面中。
点击按钮，将下载logo图片到我们的界面中。