protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_send_to_wx);
   api = WXAPIFactory.createWXAPI(this, MainActivity.WX_APP_ID, false);
   api.registerApp(MainActivity.WX_APP_ID);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
   // Inflate the menu; this adds items to the action bar if it is present.
   getMenuInflater().inflate(R.menu.menu_send_to_wx, menu);
   return true;
}
private String buildTransaction(final String type) {
   return (type == null) ? String.valueOf(System.currentTimeMillis()) : type + System.currentTimeMillis();
}

public void send_text_to_wx(View view) {
   WXTextObject textObject = new WXTextObject();
   textObject.text = "来自测试";

   WXMediaMessage msg = new WXMediaMessage();
   msg.title = "测试Title";
   msg.mediaObject = textObject;
   msg.description = "藐视";

   SendMessageToWX.Req req = new SendMessageToWX.Req();
   req.transaction = buildTransaction("text");
   req.message = msg;
   req.scene = SendMessageToWX.Req.WXSceneSession;
   api.sendReq(req);
   finish();
}