微信支付

 public class MainActivity extends Activity implements OnClickListener {
private Button submitButton;
private Button confirmButton;
private TextView textView;
private StringBuffer sb;
private Map<String,String> resultunifiedorder;
private PayReq req;
private final IWXAPI msgApi = WXAPIFactory.createWXAPI(this, null);
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    submitButton=(Button) findViewById(R.id.bt_submit_order);
    confirmButton=(Button) findViewById(R.id.bt_corfirm);
    textView=(TextView) findViewById(R.id.tv_prepay_id);
    submitButton.setOnClickListener(this);
    confirmButton.setOnClickListener(this);
    sb=new StringBuffer();
    req=new PayReq();
}
@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    switch (v.getId()) {
    case R.id.bt_submit_order:
        String urlString="https://api.mch.weixin.qq.com/pay/unifiedorder";
         PrePayIdAsyncTask prePayIdAsyncTask=new PrePayIdAsyncTask();
         prePayIdAsyncTask.execute(urlString);      //生成prepayId

    break;
    case R.id.bt_corfirm:
        genPayReq();//生成签名参数
        sendPayReq();//调起支付
    break;
    default:
        break;
    }
}
/*
 * 调起微信支付
 */
private void sendPayReq() {


    msgApi.registerApp(Constants.APP_ID);
    msgApi.sendReq(req);
    Log.i(">>>>>", req.partnerId);
}
private long genTimeStamp() {
    return System.currentTimeMillis() / 1000;
}
private void genPayReq() {

    req.appId = Constants.APP_ID;
    req.partnerId = Constants.MCH_ID;
    if (resultunifiedorder!=null) {
        req.prepayId = resultunifiedorder.get("prepay_id");
        req.packageValue = "prepay_id="+resultunifiedorder.get("prepay_id");
    }
    else {
        Toast.makeText(MainActivity.this, "prepayid为空", Toast.LENGTH_SHORT).show();
    }
    req.nonceStr = getNonceStr();
    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");

    textView.setText(sb.toString());

    Log.e("Simon", "----"+signParams.toString());

}
private String genAppSign(List<NameValuePair> params) {
    StringBuilder sb = new StringBuilder();

    for (int i = 0; i < params.size(); i++) {
        sb.append(params.get(i).getName());
        sb.append('=');
        sb.append(params.get(i).getValue());
        sb.append('&');
    }
    sb.append("key=");
    sb.append(Constants.API_KEY);

    this.sb.append("sign str\n"+sb.toString()+"\n\n");
    String appSign = MD5.getMessageDigest(sb.toString().getBytes());
    Log.e("Simon","----"+appSign);
    return appSign;
}
private class PrePayIdAsyncTask extends AsyncTask<String,Void, Map<String, String>>
{
    private ProgressDialog dialog;
    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();
        dialog = ProgressDialog.show(MainActivity.this, "提示", "正在提交订单");

    }
    @Override
    protected Map<String, String> doInBackground(String... params) {
        // TODO Auto-generated method stub
        String url=String.format(params[0]);
        String entity=getProductArgs();
        Log.e("Simon",">>>>"+entity);
        byte[] buf=Util.httpPost(url, entity);
        String content = new String(buf);
        Log.e("orion", "----"+content);
        Map<String,String> xml=decodeXml(content);

        return xml;
    }

    @Override
    protected void onPostExecute(Map<String, String> result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        if (dialog != null) {
            dialog.dismiss();
        }
        sb.append("prepay_id\n"+result.get("prepay_id")+"\n\n");
        textView.setText(sb.toString());
        resultunifiedorder=result;
    }
}

public Map<String,String> decodeXml(String content) {

    try {
        Map<String, String> xml = new HashMap<String, String>();
        XmlPullParser parser = Xml.newPullParser();
        parser.setInput(new StringReader(content));
        int event = parser.getEventType();
        while (event != XmlPullParser.END_DOCUMENT) {

            String nodeName=parser.getName();
            switch (event) {
            case XmlPullParser.START_DOCUMENT:

                break;
            case XmlPullParser.START_TAG:

                if("xml".equals(nodeName)==false){
                    //实例化student对象
                    xml.put(nodeName,parser.nextText());
                }
                break;
            case XmlPullParser.END_TAG:
                break;
            }
            event = parser.next();
        }

        return xml;
    } catch (Exception e) {
        Log.e("Simon","----"+e.toString());
    }
    return null;

}
private String getProductArgs() {
    // TODO Auto-generated method stub
    StringBuffer xml=new StringBuffer();
    try {
        String nonceStr=getNonceStr();
        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", "https://www.baidu.com"));//写你们的回调地址
        packageParams.add(new BasicNameValuePair("out_trade_no",genOutTradNo()));
        packageParams.add(new BasicNameValuePair("total_fee", "1"));
        packageParams.add(new BasicNameValuePair("trade_type", "APP"));

        String sign=getPackageSign(packageParams);
        packageParams.add(new BasicNameValuePair("sign", sign));
        String xmlString=toXml(packageParams);
        return xmlString;
    } catch (Exception e) {
        // TODO: handle exception
        return null;
    }
}
//生成订单号,测试用，在客户端生成
private String genOutTradNo() {
    Random random = new Random();
//      return "dasgfsdg1234"; //订单号写死的话只能支付一次，第二次不能生成订单
    return MD5.getMessageDigest(String.valueOf(random.nextInt(10000)).getBytes());
}
//生成随机号，防重发
    private String getNonceStr() {
    // TODO Auto-generated method stub
    Random random=new Random();

    return MD5.getMessageDigest(String.valueOf(random.nextInt(10000)).getBytes());
}
/**
 生成签名
 */

private String getPackageSign(List<NameValuePair> params) {
    StringBuilder sb = new StringBuilder();

    for (int i = 0; i < params.size(); i++) {
        sb.append(params.get(i).getName());
        sb.append('=');
        sb.append(params.get(i).getValue());
        sb.append('&');
    }
    sb.append("key=");
    sb.append(Constants.API_KEY);


    String packageSign = MD5.getMessageDigest(sb.toString().getBytes()).toUpperCase();
    Log.e("Simon",">>>>"+packageSign);
    return packageSign;
}
/*
 * 转换成xml
 */
private String toXml(List<NameValuePair> params) {
    StringBuilder sb = new StringBuilder();
    sb.append("<xml>");
    for (int i = 0; i < params.size(); i++) {
        sb.append("<"+params.get(i).getName()+">");


        sb.append(params.get(i).getValue());
        sb.append("</"+params.get(i).getName()+">");
    }
    sb.append("</xml>");

    Log.e("Simon",">>>>"+sb.toString());
    return sb.toString();
}

}