ConnectivityManager判断是否有网络

/** 判断是否有网络 */
	private boolean checkNetwork() {
		boolean flag = false;
		ConnectivityManager cwjManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
		if (cwjManager.getActiveNetworkInfo() != null)
			flag = cwjManager.getActiveNetworkInfo().isAvailable();
		if (!flag) {
			Builder b = new AlertDialog.Builder(this).setTitle("没有可用的网络").setMessage("请开启GPRS或WIFI网络连接");
			b.setPositiveButton("确定", new DialogInterface.OnClickListener() {
				public void onClick(DialogInterface dialog, int whichButton) {
					Intent mIntent = new Intent("/");
					ComponentName comp = new ComponentName("com.android.settings",
							"com.android.settings.WirelessSettings");
					mIntent.setComponent(comp);
					mIntent.setAction("<span class=\"hilite\">android</span>.intent.action.VIEW");
					startActivity(mIntent);
				}
			}).setNeutralButton("取消", new DialogInterface.OnClickListener() {
				public void onClick(DialogInterface dialog, int whichButton) {
					dialog.cancel();
				}
			}).create();
			b.show();
		}

		return flag;
	}

Android编程获取网络连接状态(3G/Wifi)及调用网络配置界面
http://www.cnblogs.com/mainroadlee/archive/2011/01/11/Android_Network_State_Checking_And_Setting.html

/**
	 * 检测是否开启wify或gprs
	 * @param context
	 * @return
	 */
	public boolean checkNetwork(final Context context){
        ConnectivityManager manager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

        //mobile 3G Data Network
        State mobile = manager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState();
        //wifi
        State wifi = manager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState();
        
        //如果3G网络和wifi网络都未连接，且不是处于正在连接状态 则进入Network Setting界面 由用户配置网络连接
        if(mobile==State.CONNECTED||mobile==State.CONNECTING)
            return true;
        if(wifi==State.CONNECTED||wifi==State.CONNECTING)
        	return true;
        
        
        Builder b = new android.app.AlertDialog.Builder(context).setTitle("没有可用的网络").setMessage("请开启GPRS或WIFI网络连接");
		b.setPositiveButton("设置网络", new DialogInterface.OnClickListener() {
			public void onClick(DialogInterface dialog, int whichButton) {
				context.startActivity(new Intent(Settings.ACTION_WIRELESS_SETTINGS));//进入无线网络配置界面
//				context.startActivity(new Intent(Settings.ACTION_WIFI_SETTINGS)); //进入手机中的wifi网络设置界面
			}
		}).setNeutralButton("取消", new DialogInterface.OnClickListener() {
			public void onClick(DialogInterface dialog, int whichButton) {
				dialog.cancel();
			}
		}).create();
		b.show();
		return false;
        
    }

App自动更新之通知栏下载
http://www.cnblogs.com/qianxudetianxia/archive/2011/04/12/2010919.html