Android自动更新代码

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;

public class Update extends BaseActivity {
    public ProgressDialog pBar;
    private Handler handler = new Handler();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super .onCreate(savedInstanceState);
        setContentView(R.layout.update);
        Dialog dialog = new AlertDialog.Builder(Update. this )
                .setTitle( "系统更新" )
                .setMessage( "发现新版本，请更新！" )
                // 设置内容
                .setPositiveButton( "确定" , // 设置确定按钮
                        new DialogInterface.OnClickListener() {

                            @Override
                            public void onClick(DialogInterface dialog,
                                    int which) {
                                pBar = new ProgressDialog(Update. this );
                                pBar.setTitle( "正在下载" );

                                pBar.setMessage( "请稍候..." );
                                pBar.setProgressStyle(ProgressDialog.STYLE_SPINNER);
                                downFile( "http://url:8765/OA.apk" );

                            }

                        })
                .setNegativeButton( "取消" , new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int whichButton) {
                        // 点击"取消"按钮之后退出程序

                    }
                }).create(); // 创建
        // 显示对话框
        dialog.show();

    }

    void downFile( final String url) {
        pBar.show();

        new Thread() {
            public void run() {
                HttpClient client = new DefaultHttpClient();
                // params[0]代表连接的url
                HttpGet get = new HttpGet(url);
                HttpResponse response;
                try {
                    response = client.execute(get);
                    HttpEntity entity = response.getEntity();
                    long length = entity.getContentLength();
                    InputStream is = entity.getContent();
                    FileOutputStream fileOutputStream = null ;
                    if (is != null ) {

                        File file = new File(
                                Environment.getExternalStorageDirectory(),
                                "OA.apk" );
                        fileOutputStream = new FileOutputStream(file);

                        byte [] buf = new byte [ 1024 ];

                        int ch = - 1 ;
                        int count = 0 ;
                        while ((ch = is.read(buf)) != - 1 ) {
                            // baos.write(buf, 0, ch);
                            fileOutputStream.write(buf, 0 , ch);
                            count += ch;
                            if (length > 0 ) {

                            }

                        }

                    }
                    fileOutputStream.flush();
                    if (fileOutputStream != null ) {
                        fileOutputStream.close();
                    }
                    down();
                } catch (ClientProtocolException e) {
                    // TODO Auto-generated catch block

                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

        }.start();

    }

    void down() {
        handler.post( new Runnable() {
            public void run() {
                pBar.cancel();
                update();
            }
        });

    }

    void update() {

        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.setDataAndType(Uri.fromFile( new File( "/sdcard/OA.apk" )),
                "application/vnd.android.package-archive" );
        startActivity(intent);
    }

}