Android 网络应用重点———使用HttpGet 下载apk文件并安装

本例使用HttpGet 从服务器端下载一个apk文件,然后自动将apk安装到手机上
下载文件原理： 先获得一个InputStream,读取到数据，再写入到目的地(通常写到SD卡)， 概括起来也就是先读再写
主要代码如下:

public class Main extends Activity implements OnClickListener
 {
  @Override
  public void onCreate(Bundle savedInstanceState)
  {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.main); 
   Button btnDownloadInstallApk = (Button) findViewById(R.id.btnDownloadInstallApk);
   btnDownloadInstallApk.setOnClickListener(this);
  } 
  //安装apk文件
  private void installApk(String filename)
  {
   File file = new File(filename);
   Intent intent = new Intent();
   intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
   intent.setAction(Intent.ACTION_VIEW);     //浏览网页的Action(动作)
   String type = "application/vnd.android.package-archive";
   intent.setDataAndType(Uri.fromFile(file), type);  //设置数据类型
   startActivity(intent);
  }
  @Override
  public void onClick(View view)
  {
   //下载文件  存放目的地
   String downloadPath = Environment.getExternalStorageDirectory().getPath() + "/download_cache";  
   String url = "http://192.168.1.123/oa/apk/action.apk";
   File file = new File(downloadPath);
   if(!file.exists())
    file.mkdir();
   HttpGet httpGet = new HttpGet(url);
   try
   {
    HttpResponse httpResponse = new DefaultHttpClient().execute(httpGet);
    if (httpResponse.getStatusLine().getStatusCode() == 200)
    {
     InputStream is = httpResponse.getEntity().getContent();
     // 开始下载apk文件
     FileOutputStream fos = new FileOutputStream(downloadPath + "/action.apk");
     byte[] buffer = new byte[8192];
     int count = 0;
     while ((count = is.read(buffer)) != -1)
     {
      fos.write(buffer, 0, count);
     }
     fos.close();
     is.close();
     //安装  apk 文件
     installApk(downloadPath+ "/action.apk");
    }
   } catch (Exception e){}
  }
 }