本文在Android中实现查询上海地区公共交通卡余额的功能，以卡号为关键字,其它地区不在查询范围。

先来2张效果图(本人不做UI，界面有点简单啊，莫怪莫怪)

视图文件

画了个简单的EditText用于输入卡号，Button用来确定查询

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

tools:context="com.longjingtech.ljhotelandroidapp.HotelServiceActivity">

<EditText

android:id="@+id/traffic_check_edittext"

android:hint="@string/traffic_check_hint_textview"

android:layout_marginTop="200dp"

android:layout_gravity="center"

android:gravity="center"

android:maxLength="15"

android:drawableLeft="@drawable/search"

android:layout_width="wrap_content"

android:layout_height="wrap_content" />

<Button

android:id="@+id/traffic_check_button"

android:gravity="center"

android:layout_gravity="center"

android:text="@string/traffic_check_start"

android:layout_width="wrap_content"

android:layout_height="wrap_content" />

</LinearLayout>

核心代码

//查询API地址

String requestUrl = "http://220.248.75.36/handapp/PGcardAmtServlet?arg1=";

editText = (EditText)findViewById(R.id.traffic_check_edittext);

button = (Button)findViewById(R.id.traffic_check_button);

button.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

userCardNum = editText.getText().toString();

if (userCardNum.isEmpty()) {

Toast.makeText(HotelServiceActivity.this,"卡号不能为空，请重新输入",Toast.LENGTH_SHORT).show();

}

else {

//清空输入框的内容

editText.setText("");

//start to check balance

new Thread(new Runnable() {

@Override

public void run() {

Looper.prepare();

HttpClient httpClient = new DefaultHttpClient();

HttpPost httpPost = new HttpPost(requestUrl + userCardNum);

try {

HttpResponse httpResponse = httpClient.execute(httpPost);

Log.e(TAG,"retCode: " + httpResponse.getStatusLine().getStatusCode());

if (httpResponse.getStatusLine().getStatusCode() == 200) {

htmlResponse = EntityUtils.toString(httpResponse.getEntity(),"utf-8");

/*

* 返回数据格式 null('金额')

* */

resultBalance = htmlResponse.substring(6,htmlResponse.length() - 3);

AlertDialogSingleButton.Builder builder = new AlertDialogSingleButton.Builder(HotelServiceActivity.this);

builder.setMessage("卡号" + userCardNum + "的余额为 " + resultBalance)

.setPositiveButton(R.string.vod_exit_ok, new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface dialog, int which) {

dialog.dismiss();

}

}).create().show();

}

} catch (IOException e) {

e.printStackTrace();

}

Looper.loop();

}

}).start();

}

}

});

经过测试，通过这种方法查询有一天时间的延迟，应该是查询中心与公交数据中心没有做到实时同步，不过对于用户的正常使用，完全不是问题，赶紧自己动手试试吧。