ProgressDialog 解决“第一次执行图标转动，第二次执行不转动”代码：

@Override
	protected Dialog onCreateDialog(int id) {
		switch (id) {
		case PROGRESS_DIALOG:
			progressDialog = new ProgressDialog(LoginActivity.this);
			progressDialog.setMessage("正在登陆，请稍等...");
			progressDialog.setCancelable(true);
			// 设置ProgressDialog 是否可以按退回按键取消
			return progressDialog;
		default:
			return null;
		}
	}

	@Override
	protected void onPrepareDialog(int id, Dialog dialog) {
		switch (id) {
		case PROGRESS_DIALOG:
			dialog
					.setOnDismissListener(new DialogInterface.OnDismissListener() {
						@Override
						public void onDismiss(DialogInterface dialog) {
							removeDialog(PROGRESS_DIALOG);//这个起作用
							if (progressThread != null) {
								progressThread = null;
							}
						}
					});
		}
	}