android 判断是否有可用网络

 public boolean CheckNetwork() {        boolean flag = false;    ConnectivityManager cwjManager = (ConnectivityManager) AndroidBaseActivity.self.getSystemService(Context.CONNECTIVITY_SERVICE);    if (cwjManager.getActiveNetworkInfo() != null)        flag = cwjManager.getActiveNetworkInfo().isAvailable();    if (!flag) {        Builder b = new AlertDialog.Builder( AndroidBaseActivity.self).setTitle("没有可用的网络").setMessage( AndroidBaseActivity.self.getResources().getString(R.string.net_work_message));        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("android.intent.action.VIEW");                AndroidBaseActivity.self.startActivity(mIntent);            }        }).setNeutralButton("取消", new DialogInterface.OnClickListener() {            public void onClick(DialogInterface dialog, int whichButton) {                dialog.cancel();            }        }).create();        b.show();    }    Toast.makeText(AndroidBaseActivity.self, "test", 1).show();   return flag;}

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