建立 包名.wxapi.WXPayEntryActivity 檔案，保證內容如下(WechartUtils下面會給出)：

  		import android.app.Activity;
  		import android.os.Bundle;
  		import android.util.Log;
  		
  		import com.tencent.mm.opensdk.constants.ConstantsAPI;
  		import com.tencent.mm.opensdk.modelbase.BaseReq;
  		import com.tencent.mm.opensdk.modelbase.BaseResp;
  		import com.tencent.mm.opensdk.modelpay.PayResp;
  		import com.tencent.mm.opensdk.openapi.IWXAPIEventHandler;
  		
  		public class WXPayEntryActivity extends Activity implements IWXAPIEventHandler {
  		
  		    public static final String APP_ID = "";//填入自己的appid
  		    public static Back authBack;
  		
  		    public interface Back {
  		        public void onFiled(String errorMsg);
  		
  		        public void onSuccess(String code, String state);
  		    }
  		
  		    public static void registAuthBack(Back back) {
  		        authBack = back;
  		    }
  		
  		    public static void unregistAuthBack() {
  		        authBack = null;
  		    }
  		
  		    @Override
  		    protected void onCreate(Bundle savedInstanceState) {
  		        super.onCreate(savedInstanceState);
  		        WechartUtils.getInstance(this, APP_ID)
  		                .handleIntent(this, this);
  		    }
  		
  		    @Override
  		    public void onReq(BaseReq baseReq) {
  		        Log.e("-----1", "baseReq=" + baseReq);
  		    }
  		
  		    @Override
  		    public void onResp(BaseResp baseResp) {
  		        switch (baseResp.getType()) {
  		            case ConstantsAPI.COMMAND_PAY_BY_WX:
  		                if (authBack != null) {
  		                    // 0:成功; -1:錯誤; -2:使用者取消;
  		                    PayResp payResp = (PayResp) baseResp;
  		                    if (payResp.errCode == 0) {
  		                        authBack.onSuccess(String.valueOf(payResp.errCode), payResp.prepayId);
  		                    } else {
  		                        authBack.onFiled(baseResp.errStr);
  		                    }
  		                }
  		                break;
  		        }
  		        finish();
  		    }
  		
  		    @Override
  		    protected void onDestroy() {
  		        super.onDestroy();
  		        WechartUtils.getInstance(this, APP_ID)
  		                .unregisterApp(this);
  		    }
  		
  		}
 

• 建立WechartUtils檔案用於公共處理支付

  		import android.app.Activity;
  		import android.util.Log;
  		
  		import com.tencent.mm.opensdk.modelmsg.SendAuth;
  		import com.tencent.mm.opensdk.modelpay.PayReq;
  		import com.tencent.mm.opensdk.openapi.IWXAPI;
  		import com.tencent.mm.opensdk.openapi.IWXAPIEventHandler;
  		import com.tencent.mm.opensdk.openapi.WXAPIFactory;
  		
  		import java.util.concurrent.ConcurrentHashMap;
  		
  		public class WechartUtils {
  		
  		    private static final WechartUtils wechartUtils = new WechartUtils();
  		    private static final ConcurrentHashMap<String, IWXAPI> apis = new ConcurrentHashMap<>();
  		
  		    private WechartUtils() {
  		    }
  		
  		    public static WechartUtils getInstance(Activity activity, String appId) {
  		        if (activity != null
  		                && !apis.containsKey(activity.getLocalClassName())) {
  		            IWXAPI api = WXAPIFactory.createWXAPI(activity, appId, true);
  		            api.registerApp(appId);
  		            apis.put(activity.getLocalClassName(), api);
  		        }
  		        return wechartUtils;
  		    }
  		
  		    public WechartUtils handleIntent(Activity activity
  		            , IWXAPIEventHandler handler) {
  		        apis.get(activity.getLocalClassName())
  		                .handleIntent(activity.getIntent(), handler);
  		        return this;
  		    }
  		
  		    public void pay(Activity activity, String appId, String partnerId, String packageName
  		            , String prepayId, String nonceStr, String timeStamp, String sign) {
  		        if (activity == null) {
  		            return;
  		        }
  		        PayReq req = new PayReq();
  		        req.appId = appId;//appid
  		        req.partnerId = partnerId;//微信支付分配的商戶號
  		        req.packageValue = packageName;//暫填寫固定值Sign=WXPay
  		        req.prepayId = prepayId;//微信返回的支付交易會話ID
  		        req.nonceStr = nonceStr;//隨機字串
  		        req.timeStamp = timeStamp;//時間戳
  		        req.sign = sign;//簽名
  		        IWXAPI api = apis.get(activity.getLocalClassName());
  		        if (api != null) {
  		            api.sendReq(req);
  		        }
  		    }
  		
  		    public void login(Activity activity) {
  		        if (activity == null) {
  		            return;
  		        }
  		        SendAuth.Req req = new SendAuth.Req();
  		        req.scope = "snsapi_userinfo";
  		        req.state = String.valueOf(System.currentTimeMillis());
  		        IWXAPI api = apis.get(activity.getLocalClassName());
  		        if (api != null) {
  		            api.sendReq(req);
  		        }
  		    }
  		
  		    public void unregisterApp(Activity activity) {
  		        if (activity == null) {
  		            return;
  		        }
  		        IWXAPI api = apis.get(activity.getLocalClassName());
  		        if (api != null) {
  		            api.unregisterApp();
  		            apis.remove(activity.getLocalClassName());
  		        }
  		    }
  		
  		}
   
  

• 在AndroidManifest.xml檔案內註冊activity

  		<activity
  		    android:name=".wxapi.WXPayEntryActivity"
  		    android:exported="true"
  		    android:label="@string/app_name" />
  

• 建立好工具檔案後可以開始準備開發了，這裡貼出主要使用虛擬碼。

  		public class DemoActivity extends Activity {
  		    private WechartUtils wechartUtils;
  		    @Override
  		    protected void onCreate(Bundle savedInstanceState) {
  		    	//初始化工具
  		        wechartUtils = WechartUtils.getInstance(this, WXPayEntryActivity.APP_ID);
  		        //註冊微信支付回撥
  		        WXPayEntryActivity.registAuthBack(new WXPayEntryActivity.Back() {
  		            @Override
  		            public void onFiled(String errorMsg) {
  		            	//支付失敗回撥
  		            }
  		
  		            @Override
  		            public void onSuccess(String code, String state) {
  		            	//失敗成功回撥
  		            }
  		        });
  		    }
  		
  		    //開始微信支付方法
  		    private void startWechatPay() {
  		    	//去伺服器獲取簽名信息 具體返回的資訊可檢視後面的後臺開發
  		    	WXResponse response = getWXResponse();
  		    	//呼叫wechartUtils的pay方法調起微信支付。
  		    	wechartUtils.pay(this, response.appid, response.partnerid
  		                	, response.packageName, response.prepayid, response.noncestr
  		                	, response.timestamp, response.sign);
  		    }
  		
  		    @Override
  		    protected void onDestroy() {
  		    	//取消註冊
  		        wechartUtils.unregisterApp(this);
  		        WXPayEntryActivity.unregistAuthBack();
  		        super.onDestroy();
  		    }
  		
  		}