一、准备工作

1、开发平台及SDK下载

微信开放平台

https://open.weixin.qq.com

下载SDK

微信支付Demo下载

http://pay.weixin.qq.com/wiki/doc/api/app.php?chapter=11_1

2、创建应用

创建移动应用获取 AppID  AppSecret

要获取支付功能还需要开发者资质认证，300RMB/年的费用，貌似是开放平台中唯一要收费的…

3、AndroidMainfest文件修改

权限声明：

<uses-permission android:name="android.permission.INTERNET"/> 
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/> 

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>

<uses-permission android:name="android.permission.READ_PHONE_STATE"/> 

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

二、业务流程

商户系统和微信支付系统主要交互说明：

步骤1：用户在商户APP中选择商品，提交订单，选择微信支付。

步骤2：商户后台收到用户支付单，调用微信支付统一下单接口。参见【统一下单API】。

步骤3：统一下单接口返回正常的prepay_id，再按签名规范重新生成签名后，将数据传输给APP。参与签名的字段名为appId，partnerId，prepayId，nonceStr，timeStamp，package。注意：package的值格式为Sign=WXPay

步骤4：商户APP调起微信支付。api参见本章节【app端开发步骤说明】

步骤5：商户后台接收支付通知。api参见【支付结果通知API】

步骤6：商户后台查询支付结果。，api参见【查询订单API】

三、开发

1、注册应用

      final IWXAPI msgApi = WXAPIFactory.createWXAPI(this, null);

      msgApi.registerApp(Constants.APP_ID);

2、调用支付统一下单接口，并返回PrepayID

private class GetPrepayIdTask extends AsyncTask<Void, Void, Map<String,String>> {

		private ProgressDialog dialog;


		@Override
		protected void onPreExecute() {
			dialog = ProgressDialog.show(PayActivity.this, getString(R.string.app_tip), getString(R.string.getting_prepayid));
		}

		@Override
		protected void onPostExecute(Map<String,String> result) {
			if (dialog != null) {
				dialog.dismiss();
			}
			sb.append("prepay_id\n"+result.get("prepay_id")+"\n\n");
			show.setText(sb.toString());

			resultunifiedorder=result;

		}

		@Override
		protected void onCancelled() {
			super.onCancelled();
		}

		@Override
		protected Map<String,String>  doInBackground(Void... params) {

			String url = String.format("https://api.mch.weixin.qq.com/pay/unifiedorder");
			String entity = genProductArgs();

			Log.e("orion",entity);

			byte[] buf = Util.httpPost(url, entity);

			String content = new String(buf);
			Log.e("orion", content);
			Map<String,String> xml=decodeXml(content);

			return xml;
		}
	}

设置统一下单参数

private String genProductArgs() {
		StringBuffer xml = new StringBuffer();

		try {
			String	nonceStr = genNonceStr();


			xml.append("</xml>");
           List<NameValuePair> packageParams = new LinkedList<NameValuePair>();
			packageParams.add(new BasicNameValuePair("appid", Constants.APP_ID));
			packageParams.add(new BasicNameValuePair("body", "APP pay test"));
			packageParams.add(new BasicNameValuePair("mch_id", Constants.MCH_ID));
			packageParams.add(new BasicNameValuePair("nonce_str", nonceStr));
			packageParams.add(new BasicNameValuePair("notify_url", "http://121.40.35.3/test"));
			packageParams.add(new BasicNameValuePair("out_trade_no",genOutTradNo()));
			packageParams.add(new BasicNameValuePair("spbill_create_ip","127.0.0.1"));
			packageParams.add(new BasicNameValuePair("total_fee", "1"));
			packageParams.add(new BasicNameValuePair("trade_type", "APP"));


			String sign = genPackageSign(packageParams);
			packageParams.add(new BasicNameValuePair("sign", sign));


		   String xmlstring =toXml(packageParams);

			return xmlstring;

		} catch (Exception e) {
			Log.e(TAG, "genProductArgs fail, ex = " + e.getMessage());
			return null;
		}
		

	}

3、设置PayReq请求的参数，并发送支付请求

//设置PayReq请求的参数

private void genPayReq() {

		req.appId = Constants.APP_ID;
		req.partnerId = Constants.MCH_ID;
		req.prepayId = resultunifiedorder.get("prepay_id");
		req.packageValue = "prepay_id="+resultunifiedorder.get("prepay_id");
		req.nonceStr = genNonceStr();
		req.timeStamp = String.valueOf(genTimeStamp());


		List<NameValuePair> signParams = new LinkedList<NameValuePair>();
		signParams.add(new BasicNameValuePair("appid", req.appId));
		signParams.add(new BasicNameValuePair("noncestr", req.nonceStr));
		signParams.add(new BasicNameValuePair("package", req.packageValue));
		signParams.add(new BasicNameValuePair("partnerid", req.partnerId));
		signParams.add(new BasicNameValuePair("prepayid", req.prepayId));
		signParams.add(new BasicNameValuePair("timestamp", req.timeStamp));

		req.sign = genAppSign(signParams);

		sb.append("sign\n"+req.sign+"\n\n");

		show.setText(sb.toString());

		Log.e("orion", signParams.toString());

	}

//发送请求

msgApi.sendReq(req);

4、处理结果回调

实现微信API的IWXAPIEventHandler接口

api.handleIntent(getIntent(), new IWXAPIEventHandler);

在IWXAPIEventHandler的onResp(BaseResp resp)中处理请求回调

@Override
	public void onResp(BaseResp resp) {
		Log.d(TAG, "onPayFinish, errCode = " + resp.errCode);

		if (resp.getType() == ConstantsAPI.COMMAND_PAY_BY_WX) {
                        //处理PayReq的回调

			AlertDialog.Builder builder = new AlertDialog.Builder(this);
			builder.setTitle(R.string.app_tip);
			builder.setMessage(getString(R.string.pay_result_callback_msg, resp.errStr +";code=" + String.valueOf(resp.errCode)));
			builder.show();
		}
	}

Android微信支付SDK开发笔记