exactInput 函数接收这些参数
tokenIn: tokenA, tokenOut: tokenB, fee: this.obj.fee, recipient: user_address, deadline: deadline, amountIn: num, amountOutMinimum: minNum, sqrtPriceLimitX96: 0
普通ERC20代币可以正常兑换，但ERC20代币怎么兑换主链币呢
