准备工作这里就不说了，包括签约和申请APPID，附上微信开放平台APP开发步骤，不懂的同学可以参考这里：
https://pay.weixin.qq.com/wiki/doc/api/app/app.php?chapter=8_5
上面的步骤很详细，这里主要说下调起支付的注意事项。按照上面文档中说的商户服务器生成支付订单，先调用统一下单API生成预付单，获取到prepay_id后将参数再次签名传输给APP发起支付。
相关代码如下：
//商品描述
String body = "iphone6s";
//随机字符串
String nonce_str = ResourceUtil.createRandomString(32);
//通知地址
String notify_url = "http://www.weixin.qq.com/wxpay/pay.php";
//商户订单号
String out_trade_no = ResourceUtil.generateOutTradeNo(32);
//总金额(单位分)
int total_fee = 1;
String url = "https://api.mch.weixin.qq.com/pay/unifiedorder";
String sign = SignUtil.signByMD5("appid=" + Constants.APP_ID + "&body=" + body +
"&mch_id=" + Constants.MCH_ID + "&nonce_str=" + nonce_str + "¬ify_url=" + notify_url +
"&out_trade_no=" + out_trade_no + "&spbill_create_ip=127.0.0.1" +
"&total_fee=" + total_fee + "&trade_type=APP" + "&key=" + Constants.KEY).toUpperCase(Locale.getDefault());
//参数以xml格式传递
String entity = "<xml><appid>" + Constants.APP_ID + "</appid><mch_id>" + Constants.MCH_ID + "</mch_id><nonce_str>" + nonce_str +"</nonce_str><sign>" + sign +
"</sign><body>" + body + "</body><out_trade_no>" + out_trade_no + "</out_trade_no><total_fee>" + total_fee +
"</total_fee><spbill_create_ip>127.0.0.1</spbill_create_ip><notify_url>http://www.weixin.qq.com/wxpay/pay.php</notify_url><trade_type>APP</trade_type></xml>";
Log.d("entity", entity);
payButton.setEnabled(false);
Toast.makeText(PayActivity.this, "获取订单中...", Toast.LENGTH_SHORT).show();
byte[] buf = Util.httpPost(url, entity);
if (buf != null && buf.length > 0) {
String content = new String(buf);
Log.d("get server pay params:", content);
OrderResult orderResult = ResourceUtil.parseXml(new ByteArrayInputStream(content.getBytes()));
if (!TextUtils.equals(orderResult.getReturnCode(), "SUCCESS")) {
Toast.makeText(PayActivity.this, orderResult.getReturnMsg(), Toast.LENGTH_SHORT).show();
return;
}
if (!TextUtils.equals(orderResult.getResultCode(), "SUCCESS")) {
Toast.makeText(PayActivity.this, orderResult.getErrorDesc(), Toast.LENGTH_SHORT).show();
return;
}
//下单成功，调起支付
PayReq request = new PayReq();
request.appId = Constants.APP_ID;
request.partnerId = Constants.MCH_ID;
request.prepayId = orderResult.getPrepayId();
request.packageValue = "Sign=WXPay";
request.nonceStr = nonce_str;
String timeStamp = String.valueOf(System.currentTimeMillis() / 1000);
request.timeStamp = timeStamp;
request.sign = SignUtil.signByMD5("appid=" + Constants.APP_ID + "&noncestr=" + nonce_str + "&package=Sign=WXPay" +
"&partnerid=" + Constants.MCH_ID + "&prepayid=" + orderResult.getPrepayId() + "×tamp=" + timeStamp + "&key=" + Constants.KEY).toUpperCase(Locale.getDefault());
api.sendReq(request);
payButton.setEnabled(true);
}
}
}); 相关参数说明在文档上都注明了，我这里面nonce_str和out_trade_no都是我随机生成的字符创，附上我的工具类，方便大家参考。
ResourceUtil.java
package com.xylpay.sdk.pay.uikit;
import java.io.IOException;
import java.io.InputStream;
import java.util.Random;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import com.xylpay.sdk.pay.bean.OrderResult;
import android.util.Xml;
public class ResourceUtil {
public static String createRandomString(int length) {
String source = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
Random random = new Random();
StringBuilder builder = new StringBuilder();
for (int i = 0; i < length; i++) {
int position = random.nextInt(source.length());
builder.append(source.charAt(position));
}
return builder.toString();
}
public static String generateOutTradeNo(int n) {
StringBuilder builder = new StringBuilder();
Random random = new Random();
for (int i = 0; i < n; i++) {
builder.append(random.nextInt(10));
}
return builder.toString();
}
public static OrderResult parseXml(InputStream is) {
//PULL解析xml数据
XmlPullParser parser = Xml.newPullParser();
OrderResult orderResult = null;
try {
parser.setInput(is, "UTF-8");
int type = parser.getEventType();
while(type != XmlPullParser.END_DOCUMENT) {
switch (type) {
case XmlPullParser.START_DOCUMENT:
break;
case XmlPullParser.START_TAG:
if (parser.getName().equals("xml")) {
orderResult = new OrderResult();
} else if (parser.getName().equals("return_code")) {
orderResult.setReturnCode(parser.nextText());
} else if (parser.getName().equals("return_msg")) {
orderResult.setReturnMsg(parser.nextText());
} else if (parser.getName().equals("result_code")) {
orderResult.setResultCode(parser.nextText());
} else if (parser.getName().equals("err_code_des")) {
orderResult.setErrorDesc(parser.nextText());
} else if (parser.getName().equals("prepay_id")) {
orderResult.setPrepayId(parser.nextText());
}
break;
case XmlPullParser.END_TAG:
break;
}
type = parser.next();
}
} catch(XmlPullParserException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return orderResult;
}
}
其中关于sign的生成，参数的顺序一定要严格按照上面的顺序加上key进行MD5加密，查看签名规范。
关于key的说明，这里的key是需要自己生成然后配置到微信开放平台的，参考商户支付密钥key的生成与设置进行配置，两边需要保持一致。另外，下单时，参数要以xml的格式来传递。
最后附上自己的签名算法：
SignUtil.java
package com.xylpay.sdk.pay.uikit;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class SignUtil {
public static String signByMD5(String source) {
byte[] bytes = null;
try {
MessageDigest digest = MessageDigest.getInstance("MD5");
digest.update(source.getBytes()); //更新摘要
bytes = digest.digest(); //再通过执行诸如填充之类的最终操作完成哈希计算。在调用此方法之后，摘要被重置。
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
}
StringBuilder builder = new StringBuilder(bytes.length * 2);
for (byte b : bytes) {
if ((b & 0xFF) < 0x10) { //如果为1位 前面补个0
builder.append("0");
}
builder.append(Integer.toHexString(b & 0xFF));
}
return builder.toString();
}
}
