android实现软件自动更新的步骤

package lgx.acc.updatedemo;  import java.io.File; import java.io.FileOutputStream; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL;  import android.app.AlertDialog; import android.content.Context; import android.content.DialogInterface; import android.content.Intent; import android.net.Uri; import android.os.Handler; import android.view.LayoutInflater; import android.view.View; import android.widget.ProgressBar; import android.widget.TextView;  public class UpdateManager {  // 应用程序Context  private Context mContext;  // 是否是最新的应用,默认为false  private boolean isNew = false;  private boolean intercept = false;  // 下载安装包的网络路径  private String apkUrl = "http://shouji.360tpcdn.com/360sj/tpi/20130201/"    + "com.flikie.wallpapers.gallery_4.apk";  // 保存APK的文件夹  private static final String savePath = "/sdcard/updatedemo/";  private static final String saveFileName = savePath    + "UpdateDemoRelease.apk";  // 下载线程  private Thread downLoadThread;  private int progress;// 当前进度  TextView text;  // 进度条与通知UI刷新的handler和msg常量  private ProgressBar mProgress;  private static final int DOWN_UPDATE = 1;  private static final int DOWN_OVER = 2;   public UpdateManager(Context context) {   mContext = context;  }   /**   * 检查是否更新的内容   */  public void checkUpdateInfo() {   //这里的isNew本来是要从服务器获取的，我在这里先假设他需要更新   if (isNew) {    return;   } else {    showUpdateDialog();   }  }   /**   * 显示更新程序对话框，供主程序调用   */  private void showUpdateDialog() {   AlertDialog.Builder builder = new AlertDialog.Builder(mContext);   builder.setTitle("软件版本更新");   builder.setMessage("有最新的软件包，请下载!");   builder.setPositiveButton("下载", new DialogInterface.OnClickListener() {     @Override    public void onClick(DialogInterface dialog, int which) {     showDownloadDialog();    }    });   builder.setNegativeButton("以后再说",     new DialogInterface.OnClickListener() {       @Override      public void onClick(DialogInterface dialog, int which) {       dialog.dismiss();      }     });    builder.create().show();  }   /**   * 显示下载进度的对话框   */  private void showDownloadDialog() {   AlertDialog.Builder builder = new AlertDialog.Builder(mContext);   builder.setTitle("软件版本更新");   LayoutInflater inflater = LayoutInflater.from(mContext);   View v = inflater.inflate(R.layout.progress, null);   mProgress = (ProgressBar) v.findViewById(R.id.progress);    builder.setView(v);   builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {     @Override    public void onClick(DialogInterface dialog, int which) {     intercept = true;    }   });   builder.show();   downloadApk();  }   /**   * 从服务器下载APK安装包   */  private void downloadApk() {   downLoadThread = new Thread(mdownApkRunnable);   downLoadThread.start();  }   private Runnable mdownApkRunnable = new Runnable() {    @Override   public void run() {    URL url;    try {     url = new URL(apkUrl);     HttpURLConnection conn = (HttpURLConnection) url       .openConnection();     conn.connect();     int length = conn.getContentLength();     InputStream ins = conn.getInputStream();     File file = new File(savePath);     if (!file.exists()) {      file.mkdir();     }     File apkFile = new File(saveFileName);     FileOutputStream fos = new FileOutputStream(apkFile);     int count = 0;     byte[] buf = new byte[1024];     while (!intercept) {      int numread = ins.read(buf);      count += numread;      progress = (int) (((float) count / length) * 100);       // 下载进度      mHandler.sendEmptyMessage(DOWN_UPDATE);      if (numread <= 0) {       // 下载完成通知安装       mHandler.sendEmptyMessage(DOWN_OVER);       break;      }      fos.write(buf, 0, numread);     }     fos.close();     ins.close();     } catch (Exception e) {     e.printStackTrace();    }   }  };   /**   * 安装APK内容   */  private void installAPK() {   File apkFile = new File(saveFileName);   if (!apkFile.exists()) {    return;   }   Intent intent = new Intent(Intent.ACTION_VIEW);   intent.setDataAndType(Uri.parse("file://" + apkFile.toString()),     "application/vnd.android.package-archive");   mContext.startActivity(intent);  };   private Handler mHandler = new Handler() {   public void handleMessage(android.os.Message msg) {    switch (msg.what) {     case DOWN_UPDATE:     mProgress.setProgress(progress);     break;     case DOWN_OVER:     installAPK();     break;     default:     break;    }   }   }; } 

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="vertical" >   <ProgressBar   android:id="@+id/progress"   style="?android:attr/progressBarStyleHorizontal"   android:layout_width="fill_parent"   android:layout_height="wrap_content" /> </LinearLayout> 

UpdateManager manager=new UpdateManager(MainActivity.this);   manager.checkUpdateInfo(); 

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